I'm assuming that you're able to use all the items you've unlocked through HHP plus what you've crafted yourself?
So let's say creating a house for Kitty unlocks the duck decoy and the log stool, and making a house for Bob unlocks the deer decoration and the log bench. If you make Kitty a house but not Bob, you've got the duck decoy and the log stool regardless of if you've crafted it or not. If you've crafted the log bench as well in the main game that will be unlocked too. However, if you haven't crafted the deer decoration it won't be, because you didn't build Bob's house.
...does that make any sense?
I think I made it worse
/I made those unlocked items up btw