Tiny map, very limited routes/corridors/pinch points, spawn point rotations known, audio cues built into the map (e.g. the puddles), foot steps can be heard and so on
If you watch the twitch clip your can hear the footsteps yourself FFS - https://www.twitch.tv/videos/1193168864?t=11h52m48s (right after the announcer says "10 seconds" you can hear Shotzzy drop down and go prone. In my headset it's clear where he is)
Knowing which spawn points people will pop up at after dying is key to 1on1/2on2. That dates back to Unreal Tournament and Quake. The limited lanes of the map is why they pre-fire the typical head glitch spots. Most of the time it does nothing but you won't ever see those in a "He's a hacker!!1111!!11" video.....
We all know that the 2nd clip in that YouTube video BBB cut the early part off where Aydan sees/hears the person go and camp in the corner. He's recycled it from months ago and is using it to make you watch his video BeCaUsE DrAmA
Serious question though - what will you lot say once Ricochet goes live and the pro's keep smashing people? Just whinge that the anti cheat doesn't work?
Problem is that cheating is so rampant that some people cannot see beyond that - zero trust in the idea that someone might just be really good

Hopefully the anti cheat will do something but I expect the cheat makers will get around it. If people really think that the anti cheat would detect cheats on a pro player and just ignore them because of some list then I don't know what to say...