This does make sense! Although, from a gameplay perspective, it does beg the question of whether it gives the timed hit mechanic enough purpose to be considered a necessary mechanic in this way. ("Why tap the button for max damage if I'm always gonna do max damage when I get the chance? I'd rather just get the damage!")
And while Geno, specifically, has attacks that follow this specific trait (time the button to up the damage), a lot of other attacks from the other party members always had additional follow-up animations to further show off the attacks. (Mario punch once? Nay, punch forward, then uppercut!) (Mallow, slam that cymbal, now open it up again!) (Bowser, throw Mario! ... And, er.. Throw him again!)
I feel like, perhaps, adding an additional movement/extra strike as a reward for timing your button presses would feel a little better gameplay-wise, be more visually interesting, and, in the face of fairness, give opponents a chance to punish if you unnecessarily proceed with your attack all willy-nilly.
As added bonus, maybe dictate the level of power in the follow-up strike with how well you timed the hit, so it's likely to never be the same way twice. Just something I was thinking about.