Developers can and should test their code in a high-fidelity simulator for some configurations–limiting myself to just Apple platforms, I certainly don't have every Mac, iPhone, or Apple Watch in every combination of versions in front of me. I shipped support for iPhone X and Apple Watch Series 4 without having either of those devices on hand–for the latter, as you probably know, without even recompiling it. None of my personal Macs have a Touch Bar, but that hasn't stopped me from writing code for it.

It's completely fair–actually, it should be expected–that extensions targeting standardized APIs should function correctly regardless of platform. If you're coming from a position of trying to incentivize people who largely don't care about a tiny, strange platform to begin with, locking them out entirely based on hardware requirements is frankly about the worst thing you could do to drive adoption.