It's not uncommon to have particle board under vinyl/linoleum flooring. However, that particle board is normally over another layer of plywood/planks. In other words, the particle board is not a structural member, it's there to level out the floor and give a nice smooth surface for gluing the vinyl/linoleum to, which it does quite well.
Again, particle board is not meant to be a structural product. If you want to make it stronger and water resistant, laminate it. (formica) That's what most of your kitchen counter tops are made of. Particle board underneath a formica laminate.