No it's not just his opinion, there are objective metrics like voter satisfaction efficiency that back it up.
https://www.electionscience.org/library/approval-voting-vers...
https://www.electionscience.org/library/approval-voting-vers...
There's nothing "objective" about it. Just because it's a number you can calculate doesn't make it the right number. Some people think it's a good metric for evaluating voting systems, but many others don't, and there isn't even remotely any kind of consensus that it's a good or even useful measure.