Wow, this news caught me by surprise, and I did a brief search and it seems to me that the original source is from Kicker.de right?
I saw it here: https://www.kicker.de/darum-sucht-tuchel-einen-sechser-wie-casemiro-948877/artikel
Any coach / club should want Casemiro hehehe, in my opinion he is among the best (maybe the best) defensive midfielder.
It is very clear the improvement that Manchester had after his hiring, and I don't believe the team will let the player go, nor Casemiro should want to change clubs so soon without winning a major title with the team. Even more so now that he is more used to English soccer.
I think that only if it involves a lot of money or if Bayern offers something very good in terms of cast and squad reformulation to become even stronger and be a candidate for the title of a Champions League for example.
obs - Both Bayern and Manchester will play the Champions next year
obs2 - It is easier to win the Bundesliga at Bayern than the Premier League at Manchester with the current teams
obs3 - I also think Bayern is more likely to win another champions than Manchester