To the OP, I’m not sure this is possible (but I’m not the developer.) Each field group is a post and each field in the field group is also a separate post. Not at all sure how revisions would work for this or how they could possibly be shown. Probably the reason that revisions are not supported. For things like this I use a github repo to hold changes to JSON files.
To the follow up question, I just did a quick test with a field group attached to the page post type that hides the content editor and revisions are being saved and can be restored. including custom fields.
