I think it's less about the distance and moreso the multitasking sum of several parts. Jean pulling his mind into hers is more than just communicating with his mind(it vaguely reminded me of when Jean told Emma we're no longer in your mind, your thoughts are enfolded in mine). Maybe being on her mental turf provides more veracity. And she is still actively attacking and defending in the physical plane. In fact, maybe that's why Jean did it that way, as telepaths usually are unconscious/vulnerable when they project their mind into another or to the astral plane
The artwork could have been more illustrative IMO...imaging a sequence of side-by-side panels of her spliting, a smokey pink astral figure entering the mindscape conversation with Ikaris juxtaposed with her physical actions with the X-Men and dealing with the Hex. Also the art, with Jean "dropping in" and "taking off", made it look more like Jean was the one entering and leaving Ikaris' mind rather than the stated inverse.