If FedRAMP qualification is tied to IPv6 support, you'll see every major contractor and cloud provider support it promptly.
If you look at the recent updates for cloud providers - AWS and GCP support for IPv6, Kubernetes going dual stack by default - you can see that this memo had a substantial impact.
Sometimes these things take time, but in this case, the recent memo you link to lit a fire under everyone.
Azure is so far behind on this it's silly.
I think in 2019 I was able to use IPv6 VNETs.