If it didn't happen in this match it would have happened in another match before long, it's rushed and the language used to confim he's onside is unnecessarily ambiguous. "Check complete, that's fine" could mean a number of things depending on the context, a more definitive statement such as "check complete, he's onside" or "check complete, the goal is good" needs to be used, why that isn't blatantly obvious to those implementing VAR I don't know.