However it took years for me to be conscious of the abstract thinking. I started out by thinking in my native tongue, then thinking in my native tongue and mentally translating into English, then thinking in English, before finally not thinking in any language at all.
There is no doubt that writing out or sounding out your reasoning can boost your ability to think and communicate. For example, it can promote a dialectic which can refine your ideas, and you can even have an inner dialogue using language. It can also help you form a representation of the thought process for communication.
But it can also muddle your thinking or leave you with blind spots if the language is not expressive enough or you rely on it too much. You do not need a linguistic representation of a concept in order to reason about it (well, I don't seem to and I doubt I'm special in that regard).
Just because an internally consistent language may be sufficient for basic reasoning doesn't mean it's necessary overall, or that it doesn't place a 'ceiling' on the types of thoughts you can think. I would argue that it cuts both ways.
It is definitely interesting that you seemingly get reasoning "for free" when you only optimize for language (e.g. large language models). But that is the way it would be if grammar was a more formal descendant of logic.
Maybe this is why authentic geniuses, or people capable of coming up with ideas not commonly in circulation, often have a hard time explaining their ideas (see https://kottke.org/13/05/the-three-types-of-specialist)
I guess if animals can do this, we have to options: either animals have language (even if basic) or the scientific method does not require language. I see merit in both arguments.
"Lo que solemos elevar a la categoría de meditaciones no es más que el ruido de un motor encendido." Ray Loriga
My idiomatic translation: "What we usually elevate to thinking/thoughts is only the noise of a running engine."
I also believe language is necessary for thinking. I would define thinking as following the scientific method, though. That is, thinking is not necessary to tie my shoelaces or go shopping or dance (that I consider more autopilot, maybe like system 1 and 2?). But to make a rigorous argument, IMO one needs language. Under this definition of thinking it seems logic is pretty important, and logic seems to me language-based.
I suspect that different people think verbally to different degrees. I mean, everyone uses words in their head to manipulate ideas, to some extent; but some people use pictures more than others, and some people are very abstract, and despite being super-bright, aren't very good at translating their ideas into clear language.
In looking back over this, I stumbled over this study which seems to directly contradict the one in the original link:
https://journals.sagepub.com/doi/10.1177/0956797612443836
"This study explores whether the cognitive advantage associated with bilingualism in executive functioning extends to young immigrant children challenged by poverty..."
which implies that there is a "cognitive advantage associated with bilingualism".
So maybe the original study is just bogus. Or maybe this one is. Who knows? Sociology doesn't have a stellar reputation for generating reproducible results.
Bilinguals are better than monolinguals in detecting manipulative discourse
Put another way, I think the discussion is probably at relevant as the study.
What benchmark could you possibly have for this? You have no clue what monolingual you would have been like.
Imagining a deficit in one's abilities is not hard. It's going the other way -- imagining what it would be like to be able to do something that you have never done -- that is difficult.
(In fact, I don't even have to imagine. I know what it is like to learn a language as an adult, and how different that is from learning one as a child, because I've done both.)
"You have no clue what monolingual you would have been like."
And that's not true. I have several pretty good clues. Not only that, but what I imagine about the counterfactual me leads me to be able to formulate a testable hypothesis with respect to non-counterfactual situations, namely, that acquiring multiple languages in one's youth does afford some measurable cognitive advantages in general.
You can get a lot of leverage out of imagining things.