ARN Matching Incorrectly Flags Wildcards In Region As Invalid

[squatched]

(This comment from a couple years ago seems to jive with my understanding.)

From the documentation:

You can use wildcard characters (* and ?) within any ARN segment . An asterisk (*) represents any combination of zero or more characters, and a question mark (?) represents any single character. You can use multiple * or ? characters in each segment, but a wildcard cannot span segments.

Given this policy statement:

{
    "Effect": "Allow",
    "Action": "rds:CopyDBParameterGroup",
    "Resource": "arn:aws:rds:us-west-?:0123456789012:*pg:*"
}

The linter fails with:

        Severity: MEDIUM
        Issue: INVALID_ARN
        File: <stdin>
        Detail: Region expected to be of form like us-east-1 but got ['us-west-?']

However, it is accepted and works as expected in the policy sim and as a policy in an IAM role.