The diagrams you posted show the range of frequencies which MAY be present. What energy is actually in those bands depends on the picture content.
First diagram:
In the narrow band FM of the luminance signal, the slowly varying parts of the baseband signal produce the range of frequencies from 3.5 to 4.5 MHz, as you stated. But modulation by higher frequencies (fine detail) produces the luminance sidebands shown. You really need college-level math (Bessel functions) to determine what these are. If the system does not pass these sidebands, the fine detail will be filtered out.
https://www.johndcook.com/blog/2016/...-an-fm-signal/