Hot take: What may be wrong with sbmm

I’m a plat 4, like 1.3 Kd on Xbox, I’m very slightly above average, yet I get paired with diamonds (top 2%) and preds (top 0.2%) every single game with out fail. I was paired with the number one wraith on Xbox the other day with 43k kills (vortex) I’m not even remotely that good… I have like 4k kills total

I have my opinion of sbmm (I hate it) but that’s not exactly what this is about, I want to say what I think is wrong with it.

So I made a smurf account to see how long it would take to get me booted out of the “lower tier lobbies” So I started my game and went in on every gun fight I heard ran through the groups of inexperienced players and ended up winning the game with 18 kills

the very next game I’m back in predator 20 bomb lobbies

So does that mean the player base is divided 50-50? Like I previously stated, my kd on my main is average (1.3) yet I play in crazy high tier lobbies, my smurf had a 16 kd and after only 1 game was thrown back into the upper tier of lobbies.

So I’m wondering, where is the line drawn? If you’re gonna do sbmm why is it only:

“you’re in lower tier lobbies so you play with less experienced players” or “you’re a little to good to play with the lower tier players, you’ll be with diamonds and preds every game”

Because right now it seems like there’s
low gold and below lobbies
And mid gold and up lobbies,

TLDR: made a smurf, after one game of doing well was thrown right back into the predator and diamond riddled games. Is there no in between for the average players?