Yeah I had a similar experience after more or less maintaining over the Christmas holidays.
My understanding is this mostly has to do with glycogen rather than some sort of total reset. Glycogen is sugar water stored in our liver and muscles, and it’s another storage of energy for the body besides body fat. The average adult has a couple pounds of it, and most importantly glycogen is one gram of sugar bonded with three grams of water. So unlike fat that’s 3,500 calories per pound, glycogen is something like 1,500 calories for several pounds.
When we are on a deficit, the body prefers to use up the glycogen first - that is its purpose. When the sugar is gone the body lets go of the extra water it doesn’t need. This is part of why folks see dramatic scale results at the beginning of diet changes. The reverse is also true, when we have a surplus the body wants to restock on glycogen and all the water that comes with that.
This is how the scale can spike after a big treat meal despite not eating the thousands of additional calories it would require to add that much body fat. But once we’re back on our deficit we use it up again, water gets let go again.
It’s a common phenomenon, but idk the exact science behind it. Eating at a deficit is stressful on the body. Stress inhibits weight loss/encourages weight gain. Eating at or above maintenance for a couple days might help lower stress levels and remove the inhibition. I guess it’s kind of like a reset. Personally I feel like I need at least a couple days per month at maintenance.