You're talking about an extremely end of cycle resurgence. For the vast majority of the lifecycle, the 360 outsold the PS3 and had better compatibility with multiplatform games.
It's true the devs have become more comfortable develeoping games as the console matured but that's about it.
Xbox was always flop comparing to PS
For PS3 vs 360, the PS3 sold 87.40M units to the 360's 85.73M.
In this case, better to reduce early sales which are sold at a loss (production being expensive, significant R&D, scale being low), maximise at the end of the life when i assume they are maximising profits per console due to scale and R&D already being covered.
So, no -- it is never better to reduce early sales. You want to sell as many units as possible, as many games as possible, as many accessories as possible, as soon as possible.
(Also, as the same console does becomes cheaper to manufacture over the years, the price tends to go down as well.)
The PS3 started outselling the Xbox 360 for the year in 2007 and kept steadily gaining on the Xbox in total sales for the generation until it overtook it.
Xbox's one year head start kept it level with the PlayStation 3 for quite a while but it lost out in the end.
Look at the global yearly sales figures on VGChartz. From 2007 the PS3 outsold the Xbox 360 every year except for 2008:
The charts you link to show game sales that lag way behind the xbox. For example Skyrim sold 2.6 million in 2011 on the xbox and only a million on the ps3.
I only say this because I got my ps3 for free with the purchase of a Sony television at a Sony store (remember those?) in late 2009 and never purchased more than a bare handful of games which I almost never played.
After the cost-reduced redesign in 2009 Sony gave away a free ps3 with every television purchase in Sony stores for almost an entire year.
Skyrim was one the games I bought and it was so buggy, even for Bethesda, on the ps3 due to ram limitations (I've read) that I purchased it again for pc.
Used my ps3 to watch a ton of blurays and Netflix, though. My ps3 was, and based on those yearly charts a lot of other peoples' ps3s were also, extremely powerful streaming boxes and I only retired mine when I upgraded to a 4k tv and got an appletv 4k.
As you write later, Skyrim sucked on PS3 (like other multiplatform games like Bayonetta). It is not strange that it sold much less since it was a much worser game on the PS3.
You have to consider total software sales, not individual titles. And for the PS3 you have to consider its impact on blu-ray movie sales (which aren't in those charts).
Blu-ray also launched in 2006 and the PS3 was one of the most useful players available because it could do more than just play movies.
I think it wasnt a big deal in the rest of the world. Then Microsoft console focused on "doning more that just play" and flopped worldwide.