>>47768222Because Rock is a horrible defensive typing and cannot be compared to water. Both Water and Steel are great defensive typing but Poison is just extra for Pex at this point. Add on regenerator/recover to the mix and your set.
Even if Bastiodon was made Pure Steel, which would have been fine despite Fire, Ground and Fighting being very common, without a proper recovery move he would still be a sitting duck for a stall mon.
