Last night, I played with a tank who'd deranked from GM 2 to Plat 4 this season. We lost. I looked again later, and they'd gone down to Gold 1. Is this possible to do legitimately?

Replay code: NAPJC2

I was Cat. I goofed pretty bad a couple of times. Biggest thing (besides the braindead death to Cassidy nade crossing lanes to try to purr tank) was neglecting to do any point contesting silly bugger stuff on first. I'm plat 3 currently. I got there after a big winning streak from gold 4, which I got to after a big losing streak from plat 3.

Seems to me that the tank (starting on offense as Orisa) played like a legit GM player. Even rushing enemy spawn seems like a GM instinct thing (inevitably suicidal in plat). Two things that stood out to me as odd were the bizarre passivity on Orisa to start (albeit with stellar aim and cooldown cycling), and the full-blown retreat from choke in the extra round, which I don't understand the trigger for.

I actually complimented the tank on their Winston ahead of extra rounds. I thought they were just a normal plat tank who happened to have really good Winston instincts. Instead they were top500 last season and consistently finish in GM.

I'm curious what people think is going on here? (Also, any specific notes on my Cat would be welcome)