For what it’s worth, Jason Lisle is probably best known for his work on what he calls the Anisotropic Synchrony Convention.
This cites the fact (which is actually true) that we can’t measure the speed of light in a single direction, and so, thanks to special relativity, we could come up with a convention in which the speed of light travelling towards us was infinite, and the speed of light travelling away from us was c/2. Hence, in that convention, light from distant stars could indeed be only six thousand years old rather than 4.5 billion.
Unfortunately, there are several problems with this.
First: it isn’t young earth creationism; it’s day-age creationism pretending to be young earth creationism. You still end up with the simplest, most obvious reference frame showing that light from distant stars has taken billions of years to travel towards us. Since YEC insists that the days of creation have to be 24 hour solar days of Earth time in Earth’s reference frame, Lisle’s ASC simply is not consistent with that insistence.
Second: It doesn’t account for the fact that light from distant stars arrives showing us things such as this:
This is a photograph from the Hubble Space Telescope showing two galaxies in collision with each other. Besides being about 300 million light years away, these two galaxies are about 100,000 light years from one side of the left hand one to the end of the “tail” of the right hand one, and are colliding with each other at a rate of a couple of hundred kilometres a second or so. A quick back-of-the-envelope calculation here tells you that they must have been colliding with each other for several hundred million years to get into that configuration. Are we expected to believe that God created these galaxies with the appearance of being in collision with each other when in fact they weren’t?
Third: it makes the maths insanely complicated.
Fourth: it disregards the physical reality of how light actually works. The speed of light is intimately related to the relative strengths of electric and magnetic fields as a result of Maxwell’s Equations, and for light to be travelling infinitely fast towards us in one direction and at c/2 in the other direction would require the electric permittivity of a vacuum and the magnetic permeability of a vacuum to have different values at the same position in space and the same time depending on which way you’re travelling. Given that both these quantities are (a) scalar quantities with no inherent direction to them, and (b) fundamental constants of nature, such a proposition is quite simply patent nonsense.