Ugh.... Brutal_HO yes it is. DUDE, we need to share a beer so I can go over this with you. LOL!!
Your statement is not correct, THUS the need to have MORE boost to equal the SAME power at a lower cylinder pressure. This is why Turbo vehicles are necessary, say in Colorado where the air density is LOWER. You can increase the power and economy in higher elevation areas by increasing the compression but ultimately BOOSTING is necessary. Stock Cummins 6.7L engines have been seeing 28-35psi since 2007 models. So the theory it was for MORE Boost is misleading. Boost is nothing more than a measurement of the restriction across the head as seen by the intake charge going into the combustion chamber. Changing nothing else, a ported head with larger intake piping will not see more boost as the restriction to flow has been decreased as well as the flow velocity. Lowering the compression ratio effectively is like adding a larger gate to the fence so more cows can run through during a given time. Couple this with turbine vane manipulation and the throttle valve control, lets the turbo will accelerate faster to give more ultimate torque since the resistance to packing the mass is lower. The tradeoff is when you are cruising without the need for sustained torque, when you need HORSEPOWER... you get very little. Remember, torque is what gets you there but HORSEPOWER is what KEEPS you there. Another comparison is why smaller import engines have lower displacement and lower compression ratios but need more RPM with higher gear multiplication to get the same amount of work completed. FCA's marketing wanted to compete with two V8 Diesels total power numbers (Powerstroke & Duramax) and could not do so with the EPA controlled mandates, so a compromise had to be made.
It is now that I have begun tuning to keep the turbine speed up without the restriction of the exhaust and soon decreasing the restrictions in the intake elbow & heater... the velocity vs mass will play a role in helping horsepower over just peak torque on demand. I have been tuning race cars for 30+ years... it will not take me long to figure this engine out.