They rely on you being separated from the bike to deploy, and once they inflate, they deflate. They are good for primary impact, but not secondary impact.
So, low-side slow hanging on, will not likely deploy. Fast fall-off, will help on when you hit the tarmac, but not if you hit anything else. I'd like to see proper test data.
MotoGP riders use them, but those systems cost over 3 grand.
I can see forgetting you are tethered and doing a blowfish by mistake.