Microsoft has over 125 billion cash on hand[0]. I think they could spare some Azure compute to simply VPN all Windows DNS requests if they wanted (regardless of rfc8484).
I’m not saying they do. They wouldn’t even need to - they control the resolver. They could hardcode IP addresses, use domain fronting, use a CDN to proxy, load a list of IP addresses on every update check, … There are so many ways to circumvent DNS based blocking for someone that controls the resolver and network stack that it’s not even funny any more.
The fact that no one has shown that they do any of this tells you that they’re not trying very hard to circumvent blocks. Why would that change with DoH?
Microsoft doesn’t need DoH to circumvent DNS-based blocking. They control the OS and can make it do anything.