Experiments show that drag coefficient for light depends on light frequency, but light is not a plain radiowave, it's a Hopfion or a similar thing, so our intuition about its interaction with physical vacuum (ether) can be wrong. Moreover, light is an electromagnetic wave, so it propagates through physical vacuum (ether) because of non-zero capacitance and inductance of the medium. It's possible that light interacts with physical vacuum (ether) only when transitioning from one state to another OR when it is in one of two states, which explains the behavior.

PS.

For example, look at walking droplet. It interacts with the medium through it pilot wave when it bounces off, part of the time, so drag is partial and depends on frequency too.