I'll say it: they're wrong, or disingenuous. What system you start or lead development on has nothing to do with the quality of the port. The idea that developers will ignore programming practices that are good on the 360 as well as the PS3 just because they lead on the 360 doesn't make sense unless that developer just doesn't have much experience, in which case leading on a system they can't figure out in the first place probably isn't a good thing.
The idea I've seen espoused is that by utilizing best-practices for PS3 programming (i.e. achieving high levels of data locality) transfers over well to any other modern multi-core MPU design.
I agree that something about this just seems "off" though, because it implies that the reverse is also true, but we see that is clearly not the case.
I think the poor ports we've seen thus far have been a result of poor understanding of PS3 programming, and lack of development time and other resources (like actual programmers).