Okay, I believe this is the explanation:  that paragraph is in the context of making the choice to treat a nonresident alien spouse as a resident.  If a couple makes that choice they *must* file a joint return the first year they make it, but after the first year they can file MFS if they want to.  So in that context the NRA spouse needs an ITIN.

But for couples who never make that choice, the NRA spouse does not need an ITIN.

@itonewbie