You are right

He didn't hit him high or with his helmet.

The rule is ridiculous in that situation, but you're not allowed to blindside anymore. That's what he was called for, not where he hit him. And to your point, his only option in that case is simply allowing him to go and make the tackle. It's a situation where the league created a rule that does not allow you to block a would be tackler if he doesn't see you coming. Simple as that.