You can change the timing factor of input that zbrush recognizes as the space between clicks easily, try that first.
Preferences menu, Interface, Click Time and Click Distance. You can try to adjust the values there to your taste. Mine is set really high all the way to the right for Click Time and default I think for Click Distance I remember having to play around with those to get rid of the problem. This used to really annoy me as well until I edited those.
I don’t know how to disable the feature entirely if that doesn’t work for you someone else will have to chime in if that’s the case.
Last thing to play with to fine tune performance for tablet use recognition (other than the Tablet menu options) is under Preferences/Performance and Mouse and Tablet samples Per Second. Crank that up from the low default setting, mine is about 500 per second and sit amazed at the new level of tablet sensitivity to things like stroke pressure and click timing that you now possess. Try those things in combination you may hit upon the right combo to solve the resize issue which can seriously cut in to your time having to readjust all the time.