All of the questions with the get-be tag seem to be about the "get-passive" construction. For example, the top-voted question in the "get-be" tag, Why is “to get” sometimes used where “to be” could be used?, asks about "got uploaded", "got thrown", "got caught" vs "was uploaded", "was thrown", "was caught". So I think it would make sense to make get-be a synonym of get-passive.
I find "get-passive" preferable as the target because it seems slightly broader, but the possible slight difference in meaning does not seem enough to warrant the existence of separate tags. But maybe "get-be" could be better as a target because then the tag would cover a few types of similar constructions where "get" is used with something other than a past participle. What do people think?