Poor word choice on my behalf. Drift was meant in terms of sync between different channels or parallel processing paths and in reference to GP. Guitar effects (generally single channel, sequentially processed) bypass that.

That 10ms benchmark is a good one though. At that time window you've reached a full wavelength at 100Hz and it's right about the point where well practiced humans (e.g. musicians) will begin to perceive delay. It's a fascinating intersection between physics/engineering and psychology as signal latencies make the jump from being perceived as timbre to delay.