I must admit I didn’t completely understood your answer, but I think you misunderstood something.

There is no special speed. The “twin paradox” is caused by acceleration and not speed. If you accelerate to alpha centauri and come back, you will be younger than your twin brother.

Speed is always relative to another frame of reference. 0 speed relative to the CMB is not special in any way.

Since you cannot tell if A is moving (constant speed) relative to B or the opposite, also time dilatation is experienced by both A and B: A will see B click going slower and B will see A clock going slower.

Even if the article states that if you rest, you go at maximum speed on the time axis, it doesn’t mean that there is an absolute speed and going at 0 speed is “special”.

Lorentz transformations are used to calculate what a frame of reference A, considering itself a t rest, will measure of a frame B moving (constant speed) relative to A. Of course they are symmetrical and the frame B can consider itself at rest, and use Lorentz transformations to make calculations about the moving A frame.

In particular Lorentz transformations are the math behind the concept of speed of light c being constant in every frame of reference. So space and time changes in order to keep c constant, and Lorentz transformations tells you how to make the calculations.

In conclusion: acceleration is the physical parameter that makes you younger or older relative to your tween at “rest” on earth, and not speed. Note that this is also valid for gravitational acceleration.