The way I initially understood it, uppon release of the first neo rumors (then ps4k), is that sony only wanted to make a PS4K ala xboneS. Shrink the chip, add 4k movie playback, incorporate the PSVR outside box into the machine itself, and callit a day. Simultaneously, sony also had this future vision of making a 1.5 console that their new streamlined architecture aproach allowed, and maybe even easying into the rolling gen model everyone has discussed to death.
Uppon noticing that a plain shrink and a redesign with 2x the gpu grunt would cost the same, sony decided to jump into the 1.5 thing sooner, and use the grunt to render games just barely above 1080p and stretch the sucker into a 4k output so they can get a true 4k machine: movies AND games. That sequence of events is entirely my speculation, but it made sense to me. The rumors of an actual ps4 slim that plays 4k movies but not ps4neo enhancements makes all that less credible though.
With the ps slim in the picture, I do think a neo was not necessary right now. Not with sony in such a good lead. Yet, if there has to be a Neo, concentrating their message in 4k is the best aproach in my oppinion.