Unfortunately, not a giant repository of useful information you haven’t seen. It was a one-off post by an intern who had knowledge of ROBLOX internals back in 2015, so not something anyone could reasonably expect you to know.
https://devforum.roblox.com/t/do-lots-of-humanoids-cause-lag/16638/5
Humanoids always have hidden side effects because they’re a black box – we don’t know how they work. IMO this is why they should be ported to Lua , so that we not only know how they’ll impact our game, but also can tweak them elegantly without hacking around them.