My ICE CVT is like that, and hybrid systems behave sort of like CVTs.
The computer has an idea of "At this low RPM the engine is most efficient, at this high RPM it produces maximum horsepower". So if you floor it, the computer in either a CVT or a hybrid will bring the engine to full power and it will just sit there as the car accelerates.
The engine is getting loaded up and putting out more torque, and the throttle is opening, but it isn't really revving. In mine it does slowly climb from maybe 4,000 to 5,000 RPM, but it doesn't do the "rrrrRRRRRR... rrrrrrrRRRRR..." like a transmission with fixed gear ratios.
The computer has an idea of "At this low RPM the engine is most efficient, at this high RPM it produces maximum horsepower". So if you floor it, the computer in either a CVT or a hybrid will bring the engine to full power and it will just sit there as the car accelerates.
The engine is getting loaded up and putting out more torque, and the throttle is opening, but it isn't really revving. In mine it does slowly climb from maybe 4,000 to 5,000 RPM, but it doesn't do the "rrrrRRRRRR... rrrrrrrRRRRR..." like a transmission with fixed gear ratios.