I'm thinking how the couple would feel when they find out what their daughter has asked for.

I too think, if there was a party then it would've not been that awkward to ask for a certain gift, but even after spending a little while with this custom of registering at a certain store for bridal showers, baby showers, etc., I still think it is rude to even expect a gift (not that people here don't expect huge gifts ), let alone a certain gift. But then it all depends on the customs you've been exposed to I guess.