No, it doesn’t matter in PvP at all which is why their excuse for this is ridiculous. Any PvPer is going to be using addons that tell them exactly which classes are present on the other team and most PvPers are gonna have WAs for any important spells or cds going off. It’s really nonsense for them to say anyone is actually watching spell visuals to know what is happening at this point in the game.
Saying they can’t do it because of PvP is just an excuse, and an effective one at that because a lot of the PvE playerbase hates PvP and has no problem believing the excuse.