If a tick warp is currently running, and you hold down the invetoyPreview hotkey, the mspt suddenly drops (in my case it dropped from 8.5 to 5). The fps itself also drops but that's only a problem while tickwarping.
I tried doing warps of 72000 ticks with the hotkey held down all the way. The warp still proceeded as it should, the results matched those without the key held down.
This behaviour for the most part is actually useful, ie. I can tickwarp faster, but definitiely seems unintentional.
While not tickwarping the mspt is unaffected.