I am not quite sure if I can follow your reasoning correctly.
But the PC clock, as you said, was using readily available TV circuitry.
NTSC refresh rates were originally chosen to exactly match the 60 Hz of the US power grid, which helped early kinescope implementations.
Later (but still before the PC), the NTSC refresh rate was shifted
slightly downwards, to 59.94 Hz, to avoid certain audio / video issues.
I would guess that this (or something like this) eventually led to the "odd" clock in TV circuitry that the original PC then copied.
Source:
Wikipedia.