I don't disagree with you, but the opportunity for developers and publishers exists to put in less effort for Xbone and get away with it by labelling it as tough to work with where I don't think that exists with PS4 at all.
Whether it is true or not is irrelevant, it is the perception that Xbone is tougher to work with than PS4 that will stick.
We're not looking at a PS3/360 situation where the former was so difficult to work with that it was not worthwhile from a cost/benefit point of view for much of the generation bringing the PS3 version up to par. That is why developers didn't put in the effort with the PS3 version, not just because it was harder to develop for
per se and they really couldn't be arsed. Spending time on the PS3 version just represented man-hours and hence money that you probably wouldn't get returned by massively increased sales. PS4 and Xbone are both relatively straightforward architectures that are at least within the same ballpark spec-wise (by which I mean this is not a PS2/Xbox situation, or a Wii/PS360).
With a handful of exceptions, multiplatform titles this generation (and last) have generally lagged behind the best first-party exclusives, visually. That's just because you have to split development resources between two consoles and inevitably compromises have to be made in order to ship in a reasonable length of time and at a reasonable budget. If anything I would expect the gap between multiplatforms and exclusives to shrink on both consoles because of the architectural similarities between the two consoles making developing for two platforms relatively easier. I think suggesting that developers will put a lot more time and money into the PS4 version just to appease Sony fans and blame the discrepancy on a fictitiously difficult Xbone development environment is frankly somewhat absurd. If they were particularly worried about the gap between their efforts and Sony's first party they would have done it this generation.
Plus, I don't think that there really is any weight to the perception that Xbone is a prohibitively difficult development environment, outside of some extrapolation and spin by forum-goers of something that the chief architect of the PS4 said. There's no parallel with the PS3 because that was manifestly difficult to work with.