It is, I've made a list from all items I haven't catalogued yet and I've checked all items I got from requests for more than a month.
What you say is actually not true. I completed multiple deals where they actually gave me common item I hadn't catalogued yet. Today for example I gave a villager a perfect orange (request was 'orange') and she gave me a 'blue table', which isn't rare at all, but was something I had not catalogued yet.
However, and like stated in my first post, this doesn't go for every 'quest' out there! Only specific ones, where you have a personal say in the matter.
Edit: There's a chance they give you fruit or bamboo in which case, you missed out on your non-catalogued item. 
- - - Post Merge - - -
I realized it's possible to guide a villager to a specific plot by blocking all the other plots by 'Streetlights' and 'Park clocks' (public works projects')
Like many I was doing the reset trick to reset the plot space of villagers that newly move in till I come across them moving onto a space that I prefer. After doing this trick for multiple villagers I figured all the spaces a villager can potentially move into and put cheap pwp's on them.
Today I managed to land a villager exactly where I wanted in 3 tries! (First and second try were 2 spaces to the side on same piece of land).
My town looks a bit weird with all those park clocks and streetlights in the middle of nowhere, but it beats doing resets for hours in a row. When my last villager moves into the right space I'm removing them and voila - perfect town <3.
I realize this isn't new, but still something nice to put in this thread I think.
Did anyone else know this already? No idea if it's common knowledge!
