Metatags are always seen as changed.

This issue persists for me to this day.

Metatag 1.26.0
Revision Log Default 1.3.0

I am seeing a similar issue and I have Workflows enabled. I wondered if that were the issue.

On one content type (cta) with Workflows enabled,
+ Meta Tag and Content (Entity Reference Revisions) fields showing as edited when they weren't.

On another content type (ctb), also with Workflows enabled,
+ Meta Tag was enabled but was NOT in the list of updated fields.
+ Rabbit Hole, Menu link, and my Entity Reference Revisions field were.
+ Rabbit Hole did not appear in subsequent revisions, Menu Link and Entity Reference Revisions field did.
After disabling Workflows for that content type, Meta Tag and Entity Reference Revisions field remained in the default message -- still no Meta Tags.
Side note: These results did not correlate with whether the forms were collapsed or not and did not change with toggling collapse state.

On a third content type (ctc), there's no workflows enabled.
+ After adding a Meta Tag field, the default revision log DID include Meta Tag as being updated, even though it was not updated.
I then edited this content type to set Rabbit Hole to "Allow these settings to be overridden for individual entities," which then adds the Rabbit Hole form element to the edit form. After this, the immediately following result added "Updated the Rabbit Hole action, Rabbit Hole redirect response code, Rabbit Hole redirect fallback action, Announcement URL, and Meta Tags fields" -- this is actually expected because this is the FIRST time that form has appeared on the page, so it has to set defaults.
+ Additional revisions included only the field edited plus the errant Meta Tag that wasn't updated.

I am on Drupal 10.3.1, Metatag 8.x-1.26, Rabbit Hole 8.x-1.0, Entity Reference Revisions 8.x-1.11. Menu link is a core module.

If I had more play time, my approach would be to have a "verbose" module setting to output the diff to the Log Messages for each field.