United First shoulder strap?
 

So I have been flying with UA quite a bit recently and can't help but wonder everytime i hear the TO+Landing safety instruction to first class pax to fasten the shoulder strap... Presumably this is not provided because UA has decided 1st pax deserve a higher standard of safety than biz and economy??? So what is the reason that new 1st seats have this strap? Is it is use on other airlines?

yes normally with seats that are not facing forward but at an angle.
CX has them on J class seats.
Some have airbags instead.

strange... i have been in angled biz seats before, but no shoulder strap!?

Some have airbags on the seatbelt instead of the strap.