Particle board is nothing more than sawdust and glue mixed together and 'formed' into a board. So, when it gets wet, the glue is softened and the sawdust (like any 'wet piece of wood'), swells. It's just that there is a LOT of sawdust to swell. And since it can't shrink back into it's 'formed shape', it dries and flakes like, well, sawdust.
The board only needs to get wet a little. But the vinyl only adds to the problem. Instead of the moisture evaporating and such, perhaps the vinyl is trapping the moisture and you're getting more damage than you should. As far as being normal flooring in a mobile home, I can't say. You'd have to ask someone at a dealer or in the repair shop. Perhaps someone at the front desk at the park knows someone who works in this area of Mobile Home Repair. As for its general use for flooring, it's not. At one time, it was used a great deal. It's still used today in cheap furniture and for interior wall covering but it's shunned against for use on the floor.