BOOST is BOOST, regardless of turbo or supercharger...
You could not be more wrong. Boost pressure has little to do with output on a turbo system. Flow does. Boost completely ignores two very critical components- the temperature and the amount of oxygen available to mix with increased fuel flows.
Boost pressure is a measure of two things- mostly the inability of an engine to use the compressed air that is available to it and the differiential capacity of the compressor and motor at a given rpm. The only component that makes any sense to measure is the weight of the air that flows through the system- that measures the air being used. On a compressor map- it is measured in lbs/minute.
To illustrate the concept: consider a system designed compress air to flow 100 lbs/minute at ambient. If you heat the air, it becomes less dense and will flow say 50 lbs/min- engine output drops 50% as well. If you apply restricter plate into the initial ambient flow, you will also reduce flow to say 50 lbs/minute and the engine output drops 50%. If you increase the size of the pipe or cool the charge, the system flow will increase or become more dense, say 200 lbs/min, and the engine output doubles. The other scenario is to double the pressure through the restrictor plate, but still measure 100 lbs/min flow. Output is the same as before.
Power is a function of air flow. If excess air is available even at high pressure, the power (and block durability) is not affected and engine systems actually lose energy compressing air that is not used.
It took me a long time to understand the simple concept becuse I thought just as you do- when new, the Incon turbo system could generate as much power as the best superchargers at 1/2 the pressure- how could that be?.
The answer was entirely in the air flow rates through an intercooler, especially during the mid range, or torque peak, when the engine needs air the most, and a lesser extent to the parasitic power losses inherent with superchargers. That issue is conveniently ignored by supercharger manufacturer sales data.