When I was a refrigeration mechanic, I had a customer who shut his walk-in down for the winter. Every spring I would have to add refrigerant but could find no leaks. I finally realized that while it was sitting, the gaskets dried out and shrank, letting it leak. When he turned it on, the oil would hit the gaskets, swell them up and stop the leaks. After that, I told him to turn it over once a week to keep it from leaking and as far as I know, it did the trick.
All that leads up to me saying that yes, the seals might very well be swelling and stopping the leakage. Keep an eye on it for the next oil change interval and see what happens.