I guess it wont hurt

sorry I am not an expert on immigration, though pretend to be, from time to time.

My guess: it wont hurt to sigh that form. Since from WOM, it should be your last step to LPR, not much work left, i.e. from the point of WOM, you have done all necessary things, and the only thing is waiting for them to adjucate (possible one more biometrics taken).

The key point is the deal. You can fire the new one any time you like (send a letter saying your service is no longer needed), which automatically terminate him/her as the proxy.

GL