Because in SoD no one queued a single BG exept AV, this is why they had to buff honor for mark turn ins.
And no, its not uncommon to min max ur way for Exalted WSG or AB with the goal of 6minute games.
People already spend 50g in consumes per WSG / AB. DMF buff is easy to get and yes people will pick up the buff before entering the next BG.
People really underestimate how sweaty Classic PvP premades WSG and AB really are, and what is required to join a good one for min maxing, its also three times as much honor as pesky 15-18k HPH in AV… Having a 10min cd or none at all is a very bad idea, esp for the people who just want to join a WSG or AB for fun, and then up against a premade with the 10% buffs and other consumes 9/10 games.
When this sod changed happend bgs still was happening and no ppl didnt do dmfs for bgs its just a waste of time since you also have to wait for queque for next bg if you want to pick up dmf buffs.
Also lets say this would indeed been happening. Then it wouldnt change a thing really. First of all in your scenario pug vs premade it wont change a thing. you still loose to a premade as a pug even without dmf buffs.
Second of all dmf is once a month so it would be a “problem” (according to your scenario) once a month.
Third of all both wsg and ab is pretty dead. most ppl go spamm avs then just do something else when they hit their threshold.
And my last point is that it dosent have to be 10 minutes nessecarly, but it dosent have to be 4 hours etheir. Even if they made it 20-30 minutes for a cd that would be more alot better and fair and not abusive in pvp (which is again is your concern).
There are already premades on Spineshatter Horde that require you to have DMF buff, while zering as a grp with 4 disc priests with the goal of getting 40k hph.