Just to clarify, I haven't seen an official ruling but the converse would be bizarre.
1. A has 100%, B has 200%, A goes first. My first parry is not reduced, but my second is by the standard 20% and further by 100%. Fine.
2. A has 200%, B has 100%, A attacks first. My first parry is reduced by 100%, and my second is reduced by 120%. Order of incoming attacks has made a profound difference to the outcome (assuming I survive the first blow, that is, maybe she rolls really low on damage.)
If A and B attack simultaneously, how do I figure which to use? I guess simultaneous attacks already have this problem, as one of them gets parried at full chance and the other is at -20%.