When are CfnXXX added from cloud formation spec?

[roybeny]

I was under the impression that Cfn constructs, like CfnBucket for example, are auto generated from the cfn spec.
but I was surprised to see that cdk 2.32.0 (https://github.com/aws/aws-cdk/releases/tag/v2.32.0) that added support for cfn spec:
cfnspec: cloudformation spec v79.0.0 (#21053) (68f09b7)

did not include the cfn constructs for the following resources:

AWS::RolesAnywhere::TrustAnchor
AWS::RolesAnywhere::Profile

which I saw was in the cfn spec json for v79.0.0.
I was looking here:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-resource-specification.html
which is not updated to 81.0.0, but said resources were there in 79.0.0 also (not sure where the json for older version is).

Where are CfnXXX constructs being added?
until then I am using CfnResource instead.

Thank you for your help.
Roy