Stressing the Backhand grip

You can see the player in red grip switching too his BH.

Obviously we would have to see the the entire match to know for sure. I have seen players play their FH's with their BH grip when the ball is returned quickly then switch to their normal FH grip, or if they are putting allot of sides spin on their loop. This could be a case where he did not feel he had enough time to switch. But it does look like that's his normal FH.

Btw Eugene Wang hits his FH with a BH biased grip although it is very slight.

Here is an example.

WLQ has a slight bias on his BH. In this sequence you can see that he hits his BH then the ball comes back fast too his FH. Not enough time to switch so he blocks it back while still in his BH grip. Then he readjusts his grip to neutral and attempts to drives the next FH.