[Freddy]

For the official who counts the ten and chops the time, the NFHS Officials Manual (for those states that follow it--presumably not Illinois, for example) puts him in a position ". . . just above the free throw line extended and halfway between the nearer free-throw lane-line extended and the sideline." From that location a ten-second count with the hand toward the endline could be a distraction to the shooter, possibly -- especially if overdone (cf. some whose ten-second count is as if it's a closely guarded count). For 3-person C's or 2-person T's who are disengaged from the free throw play due to habitually positioning themselves waaaaaay out on the sideline, this isn't an issue cuz they're in a different zip code altogether anyway and wouldn't be distracting due to distance. But for those who stand in the NFHS prescribed place, it seems a furtive flick of the wrist semi-hidden behind the leg nearer the division line serves the situation just right. It's seen by the table and the coaches, and not distractive in any possible way to the shooter.
Not prescribed but makes sense and is taught at every camp I've ever attended: the hand used to chop time on a missed FT is the same as used to signal three-point attempt--the hand nearer the division line since it's the table who needs to see either signal.