Firstly, a client will have 10 outgoing video streams at most, not 100!
Secondly, if we consider receivers bandwidth, a client can encode 2 or 3 video streams, e.g. low, medium, and high quality video.
Secondly, if we consider receivers bandwidth, a client can encode 2 or 3 video streams, e.g. low, medium, and high quality video.
The server will send 9 video streams to each connection, but it has to process only 10 video streams since it will send the same video data to all clients, if we ignore client bandwidth.
The parent post explicitly took the client bandwidth into account, that's why it was 100 instead of 10.
But your point about 10 vs 9 still stands. Still, 81, and if you bucket into 3 tiers, that's still 27. Which at least scales linearly instead of quadratically.