Probably because must “emulation” is more like “transpilation” these days - there is a hit up front to translate into native instructions, but they are then cached and repeatedly executed like any other native instructions.

But only on Apple ARM implementations which have specific hardware built into the chip to do so (emulate the memory model), which won't be available in the future because they're dropping rosetta2..

Apple isn't dropping Rosetta 2. They say quite clearly that it's sticking around indefinitely for older applications and games.

It seems to me that Apple is simply going to require native ARM versions of new software if you want it to be signed and verified by them (which seems pretty reasonably after 5+ years).