Player A plays in open, player A gets unwanted PvP interaction from player B, player A blocks player B...possibly player B complains about not being able to find player A any longer, as if they are in PG or Solo...Yeah. You missed my point, which is that if you choose to play in an environment where you can be attacked at any time, regardless of whether you want to be attacked or are prepared for an attack, there is no point in complaining when it happens. You can't control other people. You don't know their motivations, and their motivations are irrelevant anyway. You can only control how you react to whatever they do.
This is the nature of Open. It always has been. People who are victims of PvP they didn't want to engage in often assail the motivations of those who victimize them, but this is utterly pointless. Would you demand to know why that shark bit you while you were swimming off the coast of South Africa? Of course not. Biting things is what sharks do. What on earth would make you think that you were ever safe, or should be safe, if you go swimming with them?
Seems rather straight forward to me.
Motivations appear to be irrelevant...as you say...
Player A wants to play in open without being harassed.
Player B wants PvP interaction with other players.
Open is definitely not empty...every time I log in there are other players online in Open in my friend list...
In the end, player B has less control over player A than the other way around, which is a tradeoff made in the implementation of the blocking mechanics...