Just one point to add, John:
This particular question is actually at the root of my current concern and "CANNOT LIVE WITH" stance; If we "republish" 2.0 / 2.1 with normative changes, then it is no longer .../TR/WCAG20 or .../TR/WCAG21, the revisions are normatively different (and thus, I propose .../TR/WCAG201 & .../TR/WCAG211 respectively).
As I’m sure you know but will point out for others, the official URI for WCAG 2.0 is http://www.w3.org/TR/2008/REC-WCAG20-20081211/ and https://www.w3.org/TR/WCAG20/ is just a pointer to the most recent version. Similarly for https://www.w3.org/TR/2018/REC-WCAG21-20180605/ and https://www.w3.org/TR/WCAG21/. So there definitely would be a different date version, but the group would need to decide about using the existing pointer or not.
Now, as one example, Section 508 references WCAG using the pointer URI, but clarifies that it is the Dec 11 2008 version (see https://www.access-board.gov/ict/#702.10.1).
AWK