Any prospect for a leap hour is toast by the time we need it. Over a thousand years of ossification will mean our only option is to not care about aligning clock time to the sun. So it's kinda a joke to even talk about leap hours. I'm shocked they're even mentioning such an idea, they should have declared it as a non-solution.
The resolution doesn't actually mention leap hours, just that the delta is allowed to grow up to one hour. What should happen then is to be decided by future generations.
> our only option is to not care about aligning clock time to the sun
No, an easy option is to simply shift every timezone by an hour and keep UTC intact. A ton of places already do that twice a year for daylight savings.
I never understood why we mess with UTC so much when we already have another widely used mechanism to keep the sun and clocks aligned.