In my mind that kind of post comes at best from completely naive people that confuse social media with Google to ask basic questions, and at worst someone with malicious intent to make it look like this is an open question that does not have a clear answer yet (while, as you mentioned, it totally does).
Klame
joined 1 year ago
We have known for more than a decade now that training machine learning models on huge user data sets allows to predict a lot of things with decent accuracy.
Twitter has been gathering a lot of data on all of its user, it is expected them to be able to predict interests like (and much more) this if you use their service.
No need to spy on your smartphone beside what you submit willingly https://hbr.org/2012/09/use-big-data-to-predict-your-c