That would only point to the fact that there are a number of different reasons or circumstances that can lead to a weaker console/handheld outselling a more powerful offering. If there was a common factor/factors those factor/factors would be readily apparent and readily included with each assertion of "performance doesn't matter".
The more reasons or different circumstances you can show that leads to weaker hardware outselling stronger hardware, increases the likelihood that performance as an influential feature isn't as strong as we think across market segments.
It's a pattern, but is it dependable enough to bank on? I don't think so.
There are also measurable confounding variables to talk about... I'll give one big confounding (and measurable) variable: price. Another one: release dates.
And let's not leave out the ambiguous parts about what is fair to call "more powerful." Did PS2 succeed because it was "more powerful" than the Dreamcast, or because it was "less powerful" than the Xbox and Gamecube? So which category does PS2 really fall in? And why didn't Dreamcast win the generation then? And which of these consoles is really most powerful since they all did one or the other thing better than one another?
Maybe it was it a combination of many factors? (YES)
Less power could be interdependent on other factors as well (cost, release date, available technology, etc), but that doesn't make it more important than those other factors, just because it's convenient and fashionable to say so. If anything, it makes it "less" valuable a measure, because it is too interdependent.
I think it's better to say success in the console arena has a lot to do with the good fortune of many pieces falling together in the right way and at the right time. If anything, the good fortune of massive developer support for the PS2 paved it's way to success. And I would attribute that to timing, media attention, the product itself, and consumer cost more than anything else.
To analyze any of these generations in terms of winning and losing conditions or whatever, would have to afford a case study of each generation, no less. There is too much change across generations. What did Xbox Live contribute to 360 which it did not to Xbox OG? So many questions like that which cannot be answered with a broad brush stroke.