I see nothing wrong if he wins big and decides to share his win with the platform from which he got to know about the casino. The casino, being a trusted one, deserves it too, to let them know that they are doing very well by being trustworthy and reliable. This, however, makes them also put more effort into rendering good and quality services as they have been doing because if they weren't doing such, he would not have bothered to come here to share his win with the casino for the community to see.
I think you misunderstood the point as well, the correction is not why he is sharing the win with the community, and not even an attempt to try reduce the reputation of the casino. The correction is just to ensure understanding that the game which Mr Magkaisa won in was not an original game to 1win casino.
1win deserve commendation on ensuring that Mr Magkaisa gets his money, because even though it is not an original game to the casino, if 1win has scam intentions, they can also look for reasons to not pay Mr Magkaisa, and that becomes another case of a failed withdrawal.