From what I understand and read at The Verge, the new devices would locally accept commands from any other participant in Matter protocol format. I guess that doesn’t include the way through the cloud. So Apilio would need to have a way to issue local Matter commands (through our own or another platforms hardware).
And in what might be the biggest piece of news: Google is promising that it’ll update the latest Nest Thermostat to support Matter, meaning users will be able to — in theory — control their A/C and heat setups with other Matter-certified platforms (like Siri or Alexa, pending Apple and Amazon’s own updates). Disappointingly, Google is only making that promise for the entry-level Nest Thermostat, not the more powerful Nest Learning Thermostat (at least for now).