Higher boost does not always mean that more air is being moved. If the compressor is out of it's higher efficiency islands then the compressor discharge temperatures are extremely high boost pressure will go up, but the same or less air is being moved.
To some degree pressure is a measure of restriction, but in the case of turbocharging it isn't that simple or static.
The engine presents a relatively fixed level of restriction based on some things like engine RPM (there are others, but we'll keep it simple for the sake of discussion). So if at 2500 RPM you have 25 psi of boost at 500 CFM and you put different turbo on that can move 850 CFM of air at the same engine RPM but do so with less compressor temperature and you are making 20 psi of boost you are still better off since you are getting more air in the engine at 20psi than you were at 25psi.
How many people here know how boost is created? No, this is not a trick question.