MTGNexus

I've been playing Moraug, Fury of Akoum on Magic Online and I've noticed that for each trigger I get with landfall that not only will I get an additional combat phase but it will also go to the second main phase and I get to literally cast more spells if I want and then when I pass on priority again it'll go to the next combat phase and repeat for as many times as I've triggered.
Is this an MTGO bug or is this how Moraug, Fury of Akoum actually works?

So lets say second main phase I play a Fabled Passage and also sacrifice it stacking up 2 x landfall triggers.
I'll get an additional combat phase.
After that It will then go to another main phase where I can cast spells as normal.
Then it'll go to another combat phase.
Then after that it'll go to another main phase where I can cast spells as normal again.

That sounds like a bug. Moraug, Fury of Akoum gives extra combat steps, but shouldn't be giving additional main phases too. If you play a Fabled Passage and crack it during your second main phase, you should have two combats following that, then it should go to the end step.