Maybe that's only for some people.
I have a friend that is platinum 2 or 3 and some weeks ago he got offered bonus cash to do level 2 verification. First they offered 50$, then 100$ and finally 250$. As far as I know he didn't do it, even for the 250, hopefully for him the next mail to him won't be the one you got there. On reddit I saw several posts with the same bonus offers being sent to players.
To be honest, new players already have to do some sort of KYC just to be able to deposit. Making it kind of mandatory for existing customers was only a matter of time I guess.

Edit: I asked him and he got the same email, without the bonus.