Do we have any official explanation from Toyota or any knowledgeable sources on why they detuned the engine for the Supra vs Z4?

Here are the specs for reference:

Z4 has 382 hp between 5,000 and 6,500 rpm, plus 369 lb-ft. of peak torque from 1,600 to 4,500 rpm. 0 to 60-3.9 seconds. It bests the Supra’s 4.1-second time, which makes sense since it has 47 extra horsepower and only weighs 46 extra pounds.

I know 3.9 vs 4.1 is not something anyone can feel in real world driving but under <4.0 s official does give you bragging rights. Although I do recognize that the Supra is a better deal per $ when you can get only the 4 cylinder Z4 for $50K.

Was it cost? reliability concerns? fuel efficiency? holding back for a more powerful version in the future (read:more profit)?