Meh. It’s likely they require different drivers due to different chipsets, and Apple couldn’t be bothered to write complete drivers for a discontinued model that is now over a decade old. No nefarious conspiracy here.
For comparison: You can hack modern versions of macOS to work on old MacBooks. However, trackpads on some models, but not others from the same era, have incomplete support because the internal hardware is different, even though the outward functionality is the same to the end user on older supported versions of OS X.
I thought the code bases (including code for hardware drivers) of the full desktop MacOS and iOS were essentially the same now? So wouldn't it stand to reason that when the MM1 and MM2 work exactly the same on desktop, that they could likewise enable the same functionality on iOS with very little effort? The age of the device should not matter in this case... They should support their own ecosystem of devices. A 9-year-old peripheral is really not that old. Yes, that is a long time for standalone devices like iPads and iPhones that age & slow based on continually updating software and battery degradation. But peripherals should have a MUCH longer life span, especially in a closed ecosystem like Apple's.