I am 100% certain on the first point, and if you have any proof otherwise please show it, but I imagine you will have a rough time finding any. What you probably saw was two attacks that happened close enough, like a boss special and an auto attack, and you parried/blocked one of each. That is not the same thing as them happening together on the same attack. Do you have any idea how overpowered it'd be if we actually could block/parry at the same time?
It's not really semantics. The fact that blocking also mitigates damage doesn't make parry anymore effective, and like I previously stated a high block rate actually makes parry LESS effective since it will happen less often. PLD have a far smoother damage intake thanks to blocking, but that doesn't have anything to do with the parry stat itself. You first stated that parry "counts for more" for PLD because of how it interacted with block, but that doesn't make any sense, it counts just as much for WAR if not more so. Point for point a point of parry won't be anymore effective for PLD, you are both parrying at the same amount at the same rate. Well not the exact same rate, as again block overrides parry, so a WAR will typically have an overall higher parry rate than a PLD.
Your argument is akin to saying the defense increase of gear is better for PLD because it combines with block for more mitigation.