Kip S Thorne's "Black Holes & Time Warps", 1994 paperback, p.415, Box 12.1:
... The absolute horizon is just a point when created, but it then expands smoothly, like a balloon being blown up, and emerges through the star's surface precisely when the surface shrinks through the critical circumference ... It then stops expanding, and thereafter coincides with the suddenly created apparent horizon.
I would like to propose a amenable to both theoretical exploration and, through sufficient astrophysical observation, experimental verification:
What if the absolute horizon excludes matter rather than allowing matter to pass through?
The most likely consequence would be that stars of sufficient mass for their iron cores to collapse into black holes would explode with a different signature, one likely with more explosive vigor, than they would in the standard model in which matter overtaken by the expanding absolute horizon falls into its interior to become a singularity.
In an expulsion model, collapsing core matter would still seem to "disappear" as the absolute horizon overtakes it, but the disappearance would be the result of accretion and collapse onto the expanding absolute horizon, rather than from the matter simply falling through that horizon and continuing on to become a singularity at the center of the horizon. There is a good chance (but only the math would tell) that the resulting bottleneck in the "processing" of the infalling matter would push harder on the core layers just beyond the expanding absolute horizon.
I do not know if expulsion is compatible with the original Hawking mathematical analysis that led to his concept of an expanding absolute horizon. I had been wondering if there was any self-consistent way to exclude matter from the interior of a black hole as it forms. With the exclusion tweak, the expanding-from-a-point absolute horizon concept provides exactly the dynamic structure needed. I was not expecting that.
The theoretical implication of exclusionary absolute horizons would not be complicated, just different from standard theory: Singularities would simply not exist, at least not as a result of collapsing matter. Black holes would remain very real, but would be defined solely by their event horizons, and 100% of their mass would reside in the horizon. The interior of such a construct would be a region in which traditional spacetime simply does not exist.
So: While it's too much to expect an answer to this large a question, does anyone know if the concept of exclusionary absolute horizons have been explored, and if so, what kinds of predictions it makes for supernova behaviors?