I hesitate to wade into this, since I have a lot of admiration for these two men, and I am only a mediocre speaker of Pulaar, the western dialect spoken by Fulani, whose eastern dialect is Fulfulde. I have seen several variations of this story making the rounds over the last few years, and it is full of misconceptions about the Fulani communities across the Sahel, and more generally about linguistics (and language politics) of trans-national communities. It is unfortunate that in this particular article Microsoft repeats many of the errors of the Atlantic[1], and the Letterform Archive [2], and adds its own self-congratulatory spin to it.
The first misconception is that Pulaar/Fulfulde is/was rarely written. Despite the experiences of the Barry brothers, the language has been written for hundreds of years. There are manuscripts in Arabic script that attest to this - unfortunately these are generally poorly catalogued, but BU's African Ajami Library lists 25 [3] and the British Library has several collections [4]. There is a strong historical argument that the Fulani were actually the primary instigators of literacy in pre-colonial West Africa, from the 15th and 16th centuries. The practice of writing Pulaar/Fulfulde with Arabic script did without question wane in the 20th c. - particularly among the more educated and urban communities which the Barry brothers come from. This led to decreased standardisation of the language as written in the Arabic script, especially as Fulani communities came to have stronger ties to national identities than to their transnational identity as Fulani. At the same time, the general push for literacy in languages written with Latin script in the region (mostly French and English) led to a loss in language prestige for Pulaar/Fulfulde as it had less utility as a lingua franca, and was not the language of religion, trade or politics, in the way it had been.
By the 1990's, however there was substantial linguistic work done on Pulaar/Fulfulde and a modified Latin alphabet was widely in use in the linguistic and academic community, which is currently seen on almost all Wikipedia articles on the subject. This is marked by 'hooked' letters for plosives, as in Fulɓe, which this Microsoft article writes "Fulbhe." The fact that this was not widely enough known that the Barry brothers came across it before developing a new standard for writing is testament to the fragmentation within the Fulani community, but I think it also reflects the fact that they did not come at the issue from a linguistics background. Nonetheless, this pre-existing writing standard does accurately represent all of the sounds in Pulaar/Fulfulde (and also is not much different from many other African languages in the region written with a Latin alphabet). It also was used for printing a number of books in the early 2000s, and I knew of a handful of companies regularly printing books in Pulaar in Dakar, Senegal (where it is also a minority language). I once picked up an order for 10,000 books printed in Pulaar in 2005, typeset in this commonly accepted script adapted from the Latin Alphabet.
The second major misconception of the article, is that a language needs to have its own script to be accurately represented, or that having its own script enhances the literacy rate of a language. Other comments have touched on this, so I won't dwell, but from a linguistic perspective (or even from a software language perspective) the opposite is more likely to be the case. The answer to the proliferation of different standards should almost never be to create a new standard - especially one that is not at all based on the previous standards (as Adlam is based on neither Arabic or Latin abjads/alphabets). Literacy in Pulaar/Fulfulde is almost certainly better served by doubling down on an existing standard that is accessible to those who most want to access it, rather than a new standard. There are 100-150 million Pulaar/Fulfulde speakers, so even success in the range of thousands of Fulani who recognise Adlam doesn't mean it is likely to overtake the actual pragmatic literacy of those hundreds of millions who already ready on a daily basis in Latin scripts, and could easily recognise the adapted letters.
From a political perspective, there might be a value in a new unifying standard that underscores the uniqueness of Fulɓe from their neighbours in Mauritania to Sudan. But in every one of those countries, the Fulɓe are a minority, and many of their communities are nomadic/transhumant as well, further undermining their ability to integrate or oppose existing political structures. While I applaud Adlam as a commendable assertion of identity, and a valuable potential contribution to the linguistics and typography of West African languages (should it engage constructively with the field), it is politically doomed, and unfortunately lends credence to the dictum that "a language is a dialect with an army."
Pulaar/Fulfulde is an incredibly important language, but it hasn't had an army since the fall of the Empire of Sokoto in 1903 to colonial powers. It has largely been seen as a dialect because of that, despite being one of the most widely spoken in Africa (Swahili is the only other African language with a claim to have more than 100 million native speakers).
[1] https://www.theatlantic.com/technology/archive/2016/11/the-a...
[2] https://letterformarchive.org/events/inventing-the-adlam-scr...
[3] https://open.bu.edu/handle/2144/18688
[4] https://eap.bl.uk/collection/EAP387-1