These are great numbers.
However, we have to remember that the Pro wasn't heavily promoted, had a low key announcement, was a smaller jump in technology and wasn't stocked as well as the XB1X. From a consumers perspective it's harder to persuade those people without a 4K TV to buy a console that promised 1080p when the console they already had was doing 1080p. On the other hand, it's easier to persuade people without a 4K TV to buy a console that promised 1080p when the console they already had did 900p.
The jump from least powerful to most powerful is a much easier sell.
Yep, definitely good numbers. But, like you said, the launches aren't very comparable. The XBX is pretty much all MS has been talking about for over a year, while Sony launched the Pro just a few weeks after its announcement. It's been heavily promoted for months, now. The XBX was basically launched as a new console, constantly touting the most powerful system in the world. Xbox fans disappointed in the PS4 being more powerful than the OG XBO were sure to jump on board, if only for the bragging rights.
And they definitely have much more stock for it, seeing as Sony underestimated the demand for the Pro at launch. The X is still in stock at Amazon UK. Though, it has started to slip in the hourlies. It may go back up, or it may point to front-loaded sales.