Technically you are right. I suppose there is always the chance that someone will be using 10.6gr pellets at 810fps and saying they are 7.9gr ... and weighing would sort that out.
I was more thinking of slight differences in pellets.
I shot loads over the chrono yesterday that were supposed to be 8.4gr. The readings were all around 780 fps which is 11.49 fp which is fine. The odd one ... and I mean very very few ... shot near 800 and 1 shot 804. If that was 8.4 gr then that's 12.06 fp. I'm certain it would have been more like 8.2 or even less as it was very slack in the barrel. So at 8.2gr it would have been 11.77 fp.
So ok your weighing would have sorted that ... but weighing pellets outside in wind ... that will probably give problems at those weights. Also ... at something like the Worlds with 350 shooters going through Chronos over 2 days. You don't want to hold up shooting more than a minimum ... so a quick flirt over the chrono is probably all that is possible. If 1 pellet goes over at 12.06 and the next 1 goes over at 11.5 then no problem. If 3 go over at 13 fp then that's a problem.
I'll put mine over the local club chrono as well just to make sure my chrono isn't reading low.