Pretty certain this is exactly what inovelli plans to do … single hardware platform and user changeable firmware, either Zigbee (blue series) or Matter over Thread (white series). Even as a longtime Apple user, I would vote they should not waste any dev time, resources and money to do Homekit over Thread firmware.
I have zero doubt the Matter over Thread (Matter 1.0 was only recently released into the wild) firmware software capability will be less than the Zigbee (zigbee 3.0 very mature by comparison) firmware, but that is OK and the buyer will have the ultimate choice in which firmware to use.