That's as clear a video as I've seen.
You've got two linemen walking towards him and one jogging towards him from the sideline. The guy coming off the sideline has been reporting eligible randomly all game (for other plays) and in 99.9% of plays, it's the late guy coming on who reports eligible. The ref points at #70 and nods and then walks away to tell the defense. You can't see if #70 did anything when coming off the bench a bit earlier like raising his hand like you mention.
Basically the ref knew someone was reporting, saw two people casually walking towards him and one jogging from the sideline. He assumed that the guy running in from the sideline (who has been reporting a few times earlier that game), is the guy who is actually reporting since that how it works in 99% of plays. He then points to that guy to confirm and jogs off to tell the defense.
Obviously that was a big mistake and a bad assumption, but the Lions were under no time pressure to do this and they intentionally sent 3 guys towards the ref in order to create confusion over who was reporting. They then didn't see or notice the ref pointing to #70 and nodding or if they did, didn't choose to emphatically correct the ref at that point, likely because it would give away the entire trick of the play.
Yes, the ref screwed up and he shouldn't be making assumptions over who is reporting, but if you're trying to create confusion over who is reporting by doing stuff that's not normally done, then there's only so mad you can really be when confusion is created.