This is old news, unfortunately. I have been suffering from this for a while now even on direct flights. At HEL all BUD flights have been stand arrivals, as they must bus you to the non-Schengen baggage claim area. They can's use gates at Schengen area but neither thr non-Schengen gates as airport security has nothing to do with passport-free travel...
Transit pax must collect their luggage and check them in again. Really a pain. What is worst, BUD is said to be this way until spring (!?)