Is the try mandatory after a winning TD in overtime ? Rule reference, please.
Of course not! When you say "winning TD" you are implying that team B has scored and has in effect "won" the game.
Here's the AR...3-1-3-II.
Other than on the try, Team B scores a touchdown after intercepting
a forward pass, or intercepting or recovering a backward pass or
fumble. RULING: Period and game are ended, and Team B is the
winner.