I'd love to know how they work out SBMM but I don't think there's anything majorly weird there tbf from looking at my own, I have diamond, gold and silver lobbies but then more of bronze in total from my recents. Seems a bit of a small jump between them as well when a diamond lobby is median K/D 1.15 and a silver 3 is 0.99.
There is some that are ridiculous though, no reason me and my team should be in a lobby like this when there's only like 5 out of 145 other plays in the lobby that have a higher K/D than the lowest in my team:
https://sbmmwarzone.com/lobby/17254877263764144879/player/Santos - 45 is my PB now but it wasn't even fun because the majority of them were literally that shit.
I was host too, no netduma as my pings the usual & my kills in the 4 games before it were 5, 12, 8 & 34 so it's not a case of having shit games for shit lobbies either, the game straight after that was also a bronze rated one then they've been gold since. Love to know how they do it but seems more like they just throw you in with bots sometimes for a laugh, the netduma thing has been mentioned a lot as people apparently use it in kill race tournaments and they cover their ping etc. on stream so there would be no way of telling for others which is a joke.