From what I've gleaned over the years about this it more comes down to the weight being suitable for sub 12 rifles. I had a lot of weight removed from the piston in my Hatsan 55 & then downsized the TP to make it cycle better at sub 12. It was horrible before, and way hot with a full length Titan spring too.

Not sure if this exactly the same with rammers, can't you just up the pressure in to make up for the power loss, which as you say is possibly more likely to be down to effectively short stroking it ?