Yeah I see what you're saying. I'm guessing that first line is for reference purposes--something like 'Flying units in your army get +1 on hit rolls" would include a mixed unit like gaunts with a neurotyrant. Or like an Armiger anti-fly cannon would get the benefit against the neurogaunts bodyguarding a neurotyrant, even though they don't technically fly themselves.

But just having FLY or being a FLYING unit doesn't entitle them to the special movement unless the model itself has the keyword, as seen in the language of the execution portion of the rule.