PAD explained it once, but I found it back before I knew how to do screen shots so I wasn't able to save it.
Someone asked if it was because of the enhancements or did he do it physically. PAD responded that it was both and elaborated that it the enhancements negated the unstoppability enchantment making it Juggernauts strength vs. War Hulks. IIRC, in that same interview PAD said he doesn't believe Hulk can stop Juggernaut under his own power.