Common sense says yes. . .but it's a combined action with attacking. . .as I said, I play it as reducing the bonus, before the parry, but my read of the way things work says otherwise. . .
For instance, if you make a 50% action attack, that attack executes at -50, since you are using 50% less than 100% activity to attack.
If you have 30 OB, and devote 30 to parry while making a 50% melee attack, you get 30DB and attack at -50.
it does say "All of the target's bonuses (except DB and RR) are reduced by this amount.", but table 02-09 on page 17 lists "injured more than 25%", "... 50%", "... 75%" as OB only mods, just like the reduced activity penalty only applies to OB. . .I always took the cumulative hits penalties to reflect a gradual build up of minor injuries, the way the specific crit related penalties reflect singular signifigant injuries.
If the gradual build up of general injury are an OB only penalty, I'd think that means that the penalties from specific injuries are also OB only.
Regardless, I don't play that way, but I always thought that's what the rules meant.
Then again, it's not exactly 100% clear, so I could be mistaken.