Not sure whether this is intended or not, nor if it would even affect Create in a major way, but I was messing around, trying to make my own train design, but I kept messing up. (I use multiple Minecarts for a single contraption, following polartt's example)

I had to keep destroying my trains with the wrench.

Thing is, whenever I broke my trains, it would say "Removed all couplings from minecart" or something like that.
Then I checked my inventory to get my spare super glue and lo and behold, I've already had 5 couplings sitting around in my inventory (I never crafted any).

I've also encountered this bug, it allows one to generate free minecart couplings infinitely.

Here's a demonstration of a simplified example: