This video makes an analogy between a light clock and a sound clock. Showing that a clock that bounces sound back and forth for each tick will encounter time dilation under movement similar to special relativity. It proposes that light literally is a wave in the aether and scientific consensus is suppressing this truth. It insults other physics youtubers and invites the viewer to continue with them on a new revolution in science.
I haven't watched the video. But your summary using "wave in aether" is unexpecting to me. the aether idea was tossed away a century ago when near the time it was discovered, that light travels at the same speed in all measured velocities ans directions.
I've "debunked" Dialekt videos before. That channel is dangerous.
And it's not dangerous because it would be strictly incorrect, but because they do not make their initial assumptions clear unless you watch more of their videos. They assume relative proper acceleration, which in mainstream science is currently treated mostly as "utter bollocks" as one friend of my put it.
The hostile takes against other channels is not helping either.
As a disclaimer, I have not watched the video due to being on a phone without headphones. Anyways, here is what I am getting from the thumbnail.
It looks like the argument being presented is that one observer sees light travel along a longer path than the other. The problem with saying this is that both people will measure the speed of light to be the same. This requires time to 'tick' slower in the frame observed to be moving relative to the grave that is stationary. The really fucky part of special relativity is that both observers see the other observer moving slower (general relativity will describe how the two frames reconcile when they stop moving relative to each other).