Please do not spread misinformation. Downsampling needs no additional power. Why Sony is not implementing it like Ms is another question all together. But has zero to do with power of the console
It seems as if I wasn't clear enough. Most PS4 games have broken down into modes. Favoring resolution or those favoring performance. A few games have 1080p versions that have additional graphics. The console has to have the power to render the screen and the graphics at a higher resolution to Downsample. That requires power. Either you go with what is offered at 4K or go with the 1080p solution that may have other graphical enhancements. Those that want the downsample may lose out. Sony leaves that in the Developers hands. The X1X has more power which enables them to push the same effects at a higher resolution (which in turn effects what people expect to see after downsample)
From DF Tomb Raider comparison
The Pro's 'enriched' mode also makes an appearance on Xbox One X and seems to feature a very similar visual feature set, packing in more graphical upgrades ported over from the PC version. However, the big difference here is that it's presented as an alternative 4K mode, as opposed to PS4's 1080p presentation.
Like I posted above the desired end result is decided by dev and Sony is not going to force implementation. They just leave that in the Devs hands.