PR 65963 was created because the soul list getting too long. The primary problem relating to the free lists was two fold.
a) the free list was getting too long b) we took too long to traverse a long list.
Earlier changes addressed (b). And now we can handle a long free list much better. The current changes address the way the soul allocations work.
We have had multiple previous discussions about this. They have also been summarized http://os.ott.qnx.com/wiki/index.php/Kernel:proc_free_list.