I don't know about this specific shadow ban - but I know that Twitter automatically flags a lot of things as bots/misleading etc. E.g. Michael Bloomberg is one of the fastest and reliable source for flash news. But Twitter flagged him for shadow search ban - probably because of the all caps.

Rumors from my stock market friends bubble say that it is because Twitter is secretly preparing to launch a search engine that integrates web crawling, topic-hashtag pages and famous people profiles for a year now. Idk if there is any truth to this.