Smurfing vs Other family member accounts

Before I start I’d like to state that I’m completely against smurfing and would never consider doing it.
So yesterday my little bro was playing some halo 5 on my account I saw he was having a rough time since I’m pretty high level and was obviously matching against other players in the same criteria as me. I let him make his own account with his own email address and everything by the end the only thing the two accounts had in common was the fact that it was on the same Xbox. He started up Halo 5 all excited to finally play against people who weren’t god like beings with 10.0 k/d ratio. It was fine for the first two matches, the highest he encountered was about lvl 30 which was ok. He wasn’t doing terrible but he wasn’t top of the leader boards or anything. After the first few matches things went south real fast. He got matched against the type of players I would and this is Social I’m talking about. I told him to try griffball but that was just a complete mess of spawn killing tryhards. At the end of the day I think whatever algorithm halo 5 has thought he was a smurf account which is untrue. My bro loves halo but he understandably cant stand being matched against high lvl players I hope 343 can relax whatever algorithm detects alternate accounts but do any of you have any idea how he can just play at his skill tier without really skilful player being matched against him.

Best place to look for discussion about this OP is the matchmaking feedback posts (current and archived)by Dr. Menke in the matchmaking forums. He has discussed these issues quite a bit along with 343’s plans for future updates