This is a nothing article with no real substantive information or answer to the question.
The answer is undoubtedly 1. cost, and/or 2. trade war.
As the article notes, Gorilla Glass is expensive, companies would rather not pay for it and use older versions in cheaper phones, quite frankly this is a plausible enough of a reason to not even bother writing the "article".
If the author had wanted to spend another minute thinking about it before posting, they might've realized that Corning is an American company, and Chinese smartphone makers might be hedging their bets and investing in in-house / in-country alternatives in case they get cut off by the petulant child of a country that is America.