They wrote that whole ass article and never stopped to consider that time may be both an illusion (in the sense that it is an emergent rather than a fundamental property of existence) AND necessary for the evolution of life (in the sense that other hypothetical configurations of physical laws which do not feature an emergent arrow of time may not produce life).
In regions of the set of all possible universes where the physical prerequisites of evolution were not present, nobody would be there wondering about why that is. In this region, conditions are right for life to evolve, so somebody is here to ask the question. It’s just the anthropic principle.
I believe time is as much an illusion as magnetism. Meaning, we will likely find in the future that gravity and time are parts of the same force, as we did with electromagnetism.
TLDR: Assembly Theory tries to objectively measure the minimum number of steps needed to assemble complex objects from simpler ones. By assigning a minimum time to each assembly step, a minimum time “depth” can be assigned to complex objects.