[squeaky-clean]

Wow, I've been playing keyboards for years (as a hobbyist) and never noticed this but you're 100% right. Now I can never unsee this.

[kazinator]

It more or less of has to be: the string courses are evenly spaced inside the instrument, and it probably behooves the implementation of the entire linkage from the key to the hammer to be in one plane, on-center with the string course.