I don't know what is so hard for you to understand. Xeno is saying that if the PLD is in ShO it hurts the raid. If the PLD is OTing then they have higher SwO up-time. But, if the PLD is capable of MTing with the same SwO up-time, then that point does not matter. They have the same SwO up-time regardless of MTing or OTing.

He's also saying that another point in favor of WAR is their enmity generation because BB is part of their standard rotation and RoH is ideally not a part of PLD's. But there are ways around this. The first is to have the WAR open the fight before swapping to your PLD. The second is a NIN. Context is also important. A lot of fights this tier have forced DPS down-time via mechanics or add-phases which allow tanks to enjoy some alone time with the boss. They also have forced tank swaps which allow your WAR co-tank to rebuild some of the enmity lead.