Absolute nonsense. Motors are do not care whether they are generating or consuming electrical power. It is a fundamental fact of induction that rotation in the motor creates a reverse voltage- motors literally would not work if they did not have very similar efficiency as generators.

The only differences between a motor and a generator in practice are cost optimizations and fixed-frequency optimizations. Industrial generators run at fixed speeds, unlike EV motors, so they can be built more cheaply. EV motors are not any less efficient when used to recapture power.

That is true in theory. In practice, when using the motor as a generator, the operating conditions are different, and so are the efficiencies. The load side is also different, the motor controller will not act the same way as the inertia of the car.

For example, even the simple inductance and resistance of the motor means that at the same speed and at the same load angle you will see a lower voltage at the poles of the motor when acting as a generator. When your motor has high efficiency, these differences can lead to a large absolute difference when running as a generator.

You could say the same thing about how speakers/microphones are equivalent. But it should be clear that some of those devices are tuned for outputting sound vs inputting sound, or vice versa.