Absolutely nothing prevents Meta and the other big boys from sponsoring a time standard they like for their internal systems, or just using one of the existing

Absolutely nothing prevents Meta and the other big boys from sponsoring a time standard they like for their internal systems, or just using one of the existing ones which doesn't have them. Recode your APIs to emit that standard, if you have to still use GPS time then build a box which syncs to GPS and deletes leap seconds (of course why? You can buy rack mounted atomic clocks these days which will stay perfectly accurate for hundreds of years). This is, in every way, not a problem they have to cooperate with anyone else about. EDIT: also, Unix Epoch Time, has never had leap seconds. The standard is defined as UTC exactly at the start of the Unix Epoch and ticks at 1 second since then. So from that perspective, and the perspective of every sensible internal clock system in programming, you already don't have a problem.