Yes, the speed of light cannot exceed its limitation, and as one channel stretches in length, it simply requires more time to travel that length at the constant maximum speed.
The fixed channel remains the same, and covers the unstretched distance, so the light, traveling at the same constant speed reaches the end of the unchanged channel within less time than the other channel.
Or invert the same effect for cases where one channel is compressed to a shorter length, since waves oscillate. So both circumstances may be encountered. Some photons will traverse a compressed distance at a fixed speed, other photons will traverse a stretched distance. Meanwhile, the other perpedicular path is neither stretched nor squashed, and the photons in that channel demostrate the difference when compared to the effected channel.
So no matter what happens, the rate of travel is locked at the upper limit of 186,000 miles per second, whether all of space, energy and matter is squashed in a slightly smaller volume, or expanded to fill a slightly larger volume, the relativistic distances do not change, and the rate of passage of time does not change.
The fixed channel remains the same, and covers the unstretched distance, so the light, traveling at the same constant speed reaches the end of the unchanged channel within less time than the other channel.
Or invert the same effect for cases where one channel is compressed to a shorter length, since waves oscillate. So both circumstances may be encountered. Some photons will traverse a compressed distance at a fixed speed, other photons will traverse a stretched distance. Meanwhile, the other perpedicular path is neither stretched nor squashed, and the photons in that channel demostrate the difference when compared to the effected channel.
So no matter what happens, the rate of travel is locked at the upper limit of 186,000 miles per second, whether all of space, energy and matter is squashed in a slightly smaller volume, or expanded to fill a slightly larger volume, the relativistic distances do not change, and the rate of passage of time does not change.