Does Time alignment and Phase coherency make for a better loudspeaker?

sometimes

It all depends on how the designer achieves T/P coherency. 

You cannot achieve T/P coherency with room treatments. 

i have modest specimens of 3 time-and-phase-aligned speakers -- one by magnapan, one by thiel, one by vandersteen, and they all image equally well [IOW when fed the right material they all seem to "disappear" leaving just the stereo image] to my ears but each has different requirements for listening room space and placement. the only ones that actually work in a small room, are the thiel and the maggie speakers. the vandy needs LOTS of space, no less than about a 300 sq/ft, in smaller rooms they get shouty at the crossover point [2.8kc] and totally lose their magical stereo imaging. i also have a mirage omnipolar and although i don’t guess they are time/phase-aligned, they image even better than the other 3 in my experience, again only if you give them plenty of space around them even though you can listen to them in the nearfield and get quite a spectacularly stable 3D stereo image that way with a wide sweet spot.

Room treatments do not add to coherency.  Room treatments subtract.  The speaker must produce a time or phase coherent sound field in order to produce that astonishing three dimensional soundstage.  The reflections- both airborne and the mechanical interaction between the speakers and the floor (as well as to the amps and other components) though small they may be smear the sound.  The room treatments remove those reflections to restore coherency and detail as well as bring more clarity to the bass.  That is my experience.  

No, these things don't on their own, make for a better speaker. It's not like this hasn't been studied for years. 

https://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2