I honestly don't know if its anything to do with xtreamcodes vs stalker. It seemed to make sense based on my testing, but its not something I would stake my reputation on or anything.
As for why the Formuler boxes can't do what the MAG boxes do? I have no idea. They are connecting to the server the same way, so it would make sense that they could access the information in the same way. The Buzz boxes, I thought, had a similar, though less pronounced, EPG issue. It loads page by page like the Formuler but each page loads much faster, right?
The ideal is to have some sort of full EPG download happen on startup, even if it takes a couple of minutes while it loads. I don't know if that's feasible or not. Logically it makes sense but I am not a developer so I have no idea how realistic it is on this type of portal access.