MoT's WDF

Has anyone done this? Lately I have to put in a missing cash back request for nearly every purchase I make. Rakuten keeps telling me I'll get cash back more reliably and quicker if I link my Gmail to my Rakuten account. My concern obviously is this seems like a lot of info to share. However, after reading the privacy terms (here, if anyone else can't sleep) I am willing to try it if it actually works. It seems like in many cases the "inbox data" is actually excluded from use for marketing, etc.

So, has anyone else tried this, and does it actually work better?