The 10 bar (Stock) pressure in the rear is used to prevent cavitation, although it also acts like an 'air spring' and provides extra pressure for the extension of the shock. Since the 2.5W 'stock' oil (at the same pressure) will cavitate more easily than the 10W I'm using, more pressure is now not really necessary. It may have an air spring affect, but it's pressurized to keep cavitation down and the fluid dynamics of the valving consistent. I'm already running 10W in the rear, instead of the 2.5w the shock came with (It's a Sachs). With the thicker fluid the rebound adjuster can be closed with the shock compressed and it will not extend, the same for compression. It would not do that with the stock fluid and pressure. I could run more pressure, but it doesn't feel like it's necessary. Even with only 4 bar (60 psi) it's very stiff, the adjusters have more immediate affect on the feel, and are much firmer now compared to stock pressures and oil. I actually have two rear shocks to test against each other. The other is totally stock, that I got from one of the members in this forum. My shock, with 4x thicker fluid and 60 psi in gas chamber is notably stiffer and firmer than the stock shock with normal oil/pressure. I have yet to run it so hard that it feels like it's losing hydraulic control from getting too hot.
A lot of people get onto the treadmill of 'if the book says so you must do it that way'. Which is why I run 30/32 F/R tire pressure on the street instead of the stock tire pressures (34/38) and have changed the ergonomics of the hand controls, rear sets, f/r ride heights and suspension settings to tune the bike for how I want it to feel. The factory settings and numbers are just baselines from which to deviate to make the bike do what you want it to do and ride the way you prefer. So, yeah, it works for me. Your results may vary.