My initial thought is that it’s a form of mindfulness. You have made a present, conscious decision while the bread is in front of you. You haven’t just mindlessly shoved it into your gob out of habit.
You may have also somewhat interrupted your habit by already having the bread in your flat. If your habit involved going to the store, buying the bread, then eating it — your brain may have associated the reward with the parts of the process that involve walking to the store and the purchase, rather than just the consumption. If this is the case then maybe you will decide to go to the store because you associate that behaviour with the reward, but as you already have the bread you don’t rationalize going to the store so then it’s interrupted? It might just be making it easier for you to make conscious decisions?
I would need to do some more reading to give you a more concrete answer that is grounded in research journals, but the likelihood is that there are several theories at play and your solution pulls on all of them.
Fully expect to relapse.