You mean you hit key "a", and while waiting 50ms for it to appear you tense up? No, I don't find that likely.
However, for a string of them? Yeah, could be a factor. My own trigger was mere awareness.
Just knowing it couldbe latent to excess triggered that tensing, like "stay ready."
All I'm saying is its plausible. People can, do, will respond very differently to these kinds of things. Worth investigation.
For i.e. the arrow keys, or anything interactive you will probably have to be watching for the response.