If you've ever seen someone like DFO play trem then you'd be able to see that some people honestly just play like an aimbot, they twitch around in circles and keep a steady shot on the center of their target.
Not all aimbots are like that either, when I left admin on SST a while back I was up to date on most of the aimbots and some had been ported over as trem hooks from other Quake 3 mods and were what I call "scroll bots", they don't twitch out, instead their aim accelerates to one side like it would with a moving mouse, overshoots the target, and then goes back to it, it doesn't aim dead center, it rolls around within the target's boundary box and goes off of it if the target moves too fast. Have fun spotting those ones.