Me n Dave were out on the bike when the bike started to tank slap, Dave let go of the handle bars and we used our bodyweight to keep bike in upright position, when the slapping had stopped he then put hands back on bars. If you keep hold of the bars when tank slapping it will have you off.
have had the bars snap out of my hands a few times and its pretty un-nerving. Not sure about intentionally letting go tho lol, but def wouldn’t try to fit the slap coz like you say it will wrestle you off if its having a grump.