There always seems to be an awful lot of confusion between solar power & battery power.
Solar does nothing but provide battery bank charging power, at a low rate unless a very sunny day & a large solar array. Solar does not provide 120VAC.
The generator provides 120VAC which provides power to the converter/charger, or pure charger, which in turn provide much more battery charging power than solar on the best of days. The generator simultaneously provides 120VAC to the rest of the unit the same as being on shore power.
The two are not the same & are not interchangeable.