FM Question (NI FM8 as example)

[Ross21]

What is the difference, or rather why is there a difference, between feedback (Carrier modulating itself) to Modulator modulating carrier if modulator is set to the exact same ( as far as I can see) setting as original carrier?

In the attached images one can better see what I mean. In one configuration I use the carrier to modulate itself at level '40'. In another, a modulator modulates the carrier at level '40'. In both cases the frequency and other settings are the same. So why does the spectrograph show different waveforms?

[BertKoor]

When E is modulating F, then E is not modulated and stays steady.
When modulating itself, that is no longer the case.