that would be nice, but it's impossible to do in a way where books are 100% hedged in every situation. in 99.9% of cases, i think we could assume that by the december 14th election certification, that the results have be decided. but what about that 0.01% chance? what if legal challenges (more substantial ones than seen in this election) drag out into january? if they promise in the terms a specific date and the results still aren't clear at that time, they're put between a rock and a hard place: pay out when there is uncertainty or otherwise risk massive lawsuits.

that's why it's always gonna be "at their discretion".

in fact, technically, congress can still overturn biden's electoral college win. there is already one house representative vowing to challenge it when they reconvene in january. he needs to find a republican senator to co-sign the challenge---no one has stepped up yet.
https://www.nytimes.com/2020/12/15/technology/can-trump-still-win.html