You missed this: "You may summon as many weapons as you can wield, though they disappear once they leave your possession. You can dismiss any number of weapons as a free action."

Your reason for only summoning one weapon would be if you don't want to spend all your feats on TWF.

If you want to spend them on THF instead, you're summoning one two-handed weapon (and probably dealing more damage, even if you have less enhancements).

Or if you want to spend feats on neither, you're summoning one one- (to keep a hand free) or two-handed weapon, because summoning two would give you huge attack penalties.

It thanks you for the compliment! It thinks you are well-balanced too!