ALL, due to SDV's limitations around existing locations has to do the patching at a incredibly exact point, namely after the world has been fully prepared, but before the savegame data is inserted into it.

The change in SDV 2.4 that disables UpdateTick during save loading seems to also be disabling ALL.

I added SpecialisedEvents.UnvalidatedUpdateTick for use cases like that. It's the nuclear option of events: it will run on every update tick, including while the game is reading or writing a save or running async code. This is very much 'use at your peril' and will trigger a warning in the SMAPI console. See docs on the wiki for details.