The standards side of things is true, however this can be largely solved by providing a reference implementation, given that no device manufacturer is going to implement the stack from scratch. Automated testing of firmware would also work. As for high conformance... WiFi and BT devices manage to work well enough by simply buying a tested chipset and building on that, no external testing/fees necessary.

I understand the certification if a manufacturer wants to sell a product commercially as 'Matter Certified'. For hobbyists or smaller players, pulling the reference implementation, loading it onto a cheap MCU, and calling it 'Works with Matter' would suffice.

As it stands, the latter isn't an option, because of the codesigning they've shoehorned into the spec. And for all the noise made about security, once connected to the hub the manufacturer can run whatever they like on it and send data back to their servers with very little visibility to the user.

Thread is arguably the interesting part for low power devices, and doesn't force certification. Matter is little more than a protocol spec, at the tradeoff of locked down devices and annual fees. For Matter over WiFi, I can't see any point whatsoever in using it. And for the costs of Doing Matter/Thread certification most smaller hardware startups will balk at the hundreds of thousands required to do so, and stick with WiFi/BT/Zigbee/Thread + roll their own protocol/app.