well, im not sure that comment is entirely true... i only heard it from a few guys, the heat and moisture from the oil does create gases/fumes, itll be trapped in there if theres a filter in replacement for pcv. but being that its a filter and it does vacuum in, the clean air should mix in with the fumes blah blah. then pressure is going to build up inside, since its not really getting out except through the side walls into the block.. blah blah
i havent really had experience with replacing my hose for a filter. some people say itll decrease power if your stock and have bolt ons, but some say itll increase power if your force induced.. im quite not sure if i can give you a valid answer here, but hopefully this will help a bit.