b377,
Most of the problems lie in the fact that, when discussing a subject such as this, a lot of terms such as thrust, force, power, momentum, energy, etc. are used very loosely, and as a result the discussion can easily go off on a tangent, if the terms, and their context, are not defined very clearly beforehand.
You're right, the aircraft is finally propelled by the chemical energy in the fuel being released in the engine.
But you have to be careful with the term "power"... as discussed in an earlier thread, for instance: what is "power" for a Concorde?
When it is standing at the start of the runway, with all four engines at full dry thrust, you have about 120 000 lbf thrust, but the power is... zero, because that force isn't moving.
In our current context, nothing stops one from defining the "power" of the intake as the 75% (at Mach 2) of the forward-acting force on the propulsive assembly, multiplied by the speed.
With that definition, 75% of the propulsive power comes from the intake. Nothing wrong with that statement.
The mistake being made is considering the intake as a closed system, and then considering the thrust of the intake as "free power".
This is wrong, of course... nothing would work without lots of fuel being burned each second in that engine right behind the intake, to maintain the airflow, even if the engine itself produces little thrust (8%) in the process.
Maybe we could say, that the "power", in the sense of forward-acting force x speed, is "expressed" (or finally does its "work", if you like) for 75% in the intake.
Its really a matter of semantics, or terminology... saying the intake 'produces' the power is indeed misleading, as you say.
CJ