Vocaloid does that already. That’s probably why they’ve been steering away from it.
Looking at the prior version of Synthesizer V, I see that the behavior was to display the note name of the keyboard based on the position of the keyboard. I don’t know how Vocaloid currently works, but this implementation fundamentally different that how the Tiny Vocaloid Editor presents it.
The idea of using a piano roll as an editor in a musical context isn’t unique, and there is plenty of examples of that in DAWs that predate Vocaloid. Highlighting the corresponding keyboard note based on the y position on the piano roll is also a common UI feature, not something novel by Yamaha.
Not that I’d want to go up against Yamaha’s lawyers.
Also, when you click and hold on a note it will make sound.
Thanks. You can click the note on the piano keyboard to hear the pitch, but not the note that’s being edited.