I personally dont agree with a low shot count being an advantage, but I'm also not a PRS/NRL guy. Are you?
From personal experience shooting in regular and extreme field target where offhand shots are part of the game, I'd rather have a longer gun (to a point of course) than a short little bullpup. Again, though, that's different than PRS/NRL where they're shooting off baricades and props.
My assumption here, with FX making what they're calling a PRS competition gun, is that they got some PRS guys on board and asked them what they want. A friend was at RMAC last year and told me that some big name PRS rimfire guy was shooting an FX and did rather well. I don't follow PRS or RMAC so I don't know the name of the guy my buddy was referencing, but I assume he was shooting an Impact or a Crown. Quite likely that PRS gun with an Impact in his hand threw out a couple ideas to Frederick about how to make the Impact a better PRS gun, one thing led to the next and...... Dollars to doughnuts FX put him on the payroll, paid him some consulting money, or just told him they'll get him a PRS winning gun in return for him telling them what features a PRS gun needs. So, again an assumption, I'd bet the ergonomics and general ideal of the Panthera was 100% what an actual experienced PRS guy told them he wanted.