That doesn't screw your box as long as you rev it to the correct RPM before clutching in and shifting into 1st. That's called doubleclutching and everyone had to learn how to do it before synchros were introduced.
Once you know how a gearbox works and how the synchros work, double clutching makes sense on prolonging synchro life, just like how rev matching prolongs the life of a clutch.

