Well, you can’t assume that all MBCs are using Scoutbook, so that’s the first wrinkle…
Also, remember that nobody can mark a merit badge as “approved” except a unit leader with the appropriate permissions. Parents, Scouts, and MBCs can mark it “completed”… Which leads to the second wrinkle, which is Scoutbook’s confusing usage of the term “completed” vs. “approved”. In Scoutbook, “completed” means the Scout is ready to be tested, and “approved” means an appropriate leader has confirmed the Scout’s satisfactory completion of the requirement.
Important to remember that individual MB requirements can be marked “completed”, “MBC approved”, or “Leader approved” also, and you can see who marked what approved in the requirements list.
Here’s how the requirements list shows the differences – completed, Counselor Approved, and Leader Approved.
What we’ve been doing for MBCs that aren’t using Scoutbook is asking the Scouts to snap a picture of their bluecards when they get signatures, and then one of the leaders updates the info in Scoutbook. That’s worked pretty well for us over the past couple of years.