It's been a while since I last saw someone mention that article during debates on this topic.
Admittedly, it has a catchy headline, but the article doesn't contain much substance.
Apple, for better or worse, doesn't publicly report granular-level revenue streams.
So, I can't attribute much value to some “expert” doing back-of-the-napkin calculations to get their 15 minutes of spotlight.
Does Apple sell ad space? Definitely.
Is their ad revenue or even their profits from ads substantial enough to be their core product, therefore making them an ad company? Definitely not.
It's because of this that people aren't worried by Apple’s little venture in ads because it means that there's no incentive to turn their customers into their product.
Additionally, again, for better or worse, Apple has adopted a very narrow definition of tracking.
That definition is the sharing and co-mingling of collected data from different sources.
Under this definition, Apple says it does not track people, which is true.
Apple solely uses data they collect from its services and doesn't use other company's collected data, nor does it share its own.
This means that if you like a Facebook post by a Facebook group of expectant mothers, Apple won't suddenly start advertising diapers to you.
These might seem like distinctions without a difference, but for many people, it offers peace of mind.