That is an option for true "fill", differential fill, etc. My point was if you're going to run full range in the rear for fill, then match, at the very least, the tweeters. Cone/dome materials next and cone size last. If the coaxial/matching full range is there and you have the option to tune it with a narrow bandpass to see if that is preferable, at least the matching drivers are in play, that's okay too.
It's a matter of personal preference and some simply like all the corners playing. Understanding staging without a true experience of why that might be preferable is again subjective and a learned preference. Personally, I enjoy both and tune for 3 difference listening environments. Single seat, double occupancy and a full car. Many don't have that option an opt for full front and rear.
You can certainly make the case for a good wideband in the rear instead of a coaxial. Still depends on the goal or want of the primary listener/owner.