Well PS3 didn't destroy Xbox 360, but it actually caught up in 2013, after years of efforts and great games...
That's despite launching full year later, and even longer in Europe (March 2007) and having awful price...
And he's right, Xbox Scarlet will have even worse sales compared to PS5, I'm betting on 75% to 25% between Sony & Microsoft next gen.
At this very moment with these August 17th 2019 sales it's actually 69% PS4, 31% Xbox One, that's really awful after massive success that Xbox 360 was last gen.
You kinda torpedo your last point with the start of this post, The Xbox360 launched great and a whole year ahead of the PS3... but the PS3 caught up with the X360 by the end of the generation, so it isn't like the momentum wasn't already on the side of Playstation when the PS4 launched, it was moving at a pace which undone a great first year by the X360, MS just left that console to die after Kinect was done with on it, they put their focus on Kinect2.0 and the X1 all of which were not game related focus.
What I'm saying is, Xbox as a brand was in trouble compared to the Playstation brand for the second half of the previous generation, not just when the ps4 launched.
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8