Here:
https://arstechnica.com/gaming/2016/09/microsoft-says-ps4-pro-isnt-powerful-enough-to-do-true-4k/
The reality is that 4Pro does do a lot of up-scaling with or without CBR, often with CBR to make it to 4K (1800p).
That being said the idea of marketing 4K native is poor and misleading, we're all on the same page on this one, but it fits for games that have 0 intention of creating a reconstruction pipeline. This is specifically where Penello's comments would ring true vs 4Pro.
Generally speaking, you're going to get
4K frame buffer (reconstructed, dynamic or not) of a majority of games for Scorpio. This isn't the case for 4Pro as we can see from the list of existing 4Pro enhanced titles.
http://www.neogaf.com/forum/showthread.php?t=1324251
Things will obviously change over time as more developers adopt reconstruction techniques/CBR etc but that also takes time, we'll all likely revisit this thread 3 years from now and ultimately see which marketing positions held any form truth. Forza, they are one of the few engines still using Forward rendering; they won't let go, even though the rest of the industry has moved away from it. So as much as it is a matter of 'what's better', it's a bigger question of what's better for the developers in the end. I'd like to see a lot of games go reconstructed with CBR and really push the graphical barrier; interestingly this sits with the developer and not necessarily the hardware. If there's any benefit from this crud, it's nice to know the base platform still has growth opportunities in graphical fidelity.
Lastly,
It also helps them separate Xbox One S from Xbox One X. We know that One S is a 4K media device but not capable of being True 4K. Which matters _more_ in terms of branding, vs trying to poison their competitors product. If collectively we agreed as a group that it's unlikely that users will jump ship due to power, then looking within the family of Xbox devices, this differentiator being 1S and 1X is critical.