I don't think it did officially, there were definitely server plugins that did it back in the day but AFAICT it wasn't official until this 2015 update:

https://old.reddit.com/r/GlobalOffensive/comments/37ebes/maj...

> Added trace-based visibility checks to prevent networking invisible enemy players.

If you're remembering playing with the r_drawothermodels console command to get a faux-wallhack effect, that was still subject to the engines clientside occlusion culling so it didn't show everything the client (and real cheats) were actually aware of.