I think it's just a different approach.. I've read about these pulleys not being easy to pull, have to pay for the tool and for a quality pulley (not a cheap one).
Basically what goes bad on these alternators is the clutch pulley and the regulator brushes. So a used alternator with a new pulley will have the same odds to fail at the regulator as a used alternator with a pulley still turning smooth, because both will have old regulators. As long as a used clutch pulley is smooth to turn, it will last for a good 50k miles. But of course, one should have the possibility to test himself the pulley before purchasing the alternator (so buying off Ebay is not the best bet, better from breakers)
https://www.youtube.com/watch?v=a_Pzmj0jxfw
Myself I did pull & sold a few alternators both for 2001-2004 and for 2005up (different regulator), also did play a little with the regulators. As long as the pulley/clutch assembly spins easily and smoothly, a used alternator should be a rather safe bet. I had a single bad luck with a replacement regulator (even with the Bosch brand, these are rather fragile and may last less than the original ones)
Used alternators come in two flavors: the old original ones and the already replaced ones. Even the old original ones can be still found with 100K or so miles on them and should be good for another 50K miles or so. Many owners have already replaced theirs, so getting such used alternator from the breakers should be a good bet - easy to spot with their Bosch sticker on side of the cover of the regulator. I do recommend keeping the old regulator for spare if replacing the old alternator - and also double check to get the correct regulator numbers same as the original one (look up on the Fcpeuro.com site for pics)
But in the end it really comes down to the ease of replacement: removing and replacing the whole alternator or removing the alternator and buying the tool and replacing the pulley.