It is a bit too early to judge branching and bud count. It is very usuall for a fall blooming cultivar to have far better branching and bud count with fall bloom. the later it is , the more buds. I suspect that cold weather has something to do with it. As flower stalk develops more slowly  the bud count is increased.

Also maiden bloom in fall means just that, Mainden bloom in fall. To tell if it is a rebloomer, you will need to evaluate it over  next few years to see if it blooms in spring and again in late summer or fall.  There are a fair mumber of plants that maiden bloom in fall, but  never again. Been there, done that.

As Debrenee isn't a rebloomer, my guess is that this seedling will not likely be a rebloomer. Although  Debrenee has a reblooming parent, it would seem to be a Fall Cyclic rebloomer. so genetics don't seem to match up with Immortality's genetics.  Cyclic  rebloom genes  acts like a dominant, so Debreenee is not a carrier of those genes, ele it would be a cyclic rebloomer. Immortality is a summer , or direct rebloomer, so different sets of genes.


But, time will tell. Worth keeping for further  evaluation.

Chuck Chapman