It's very smart business by Souths. Barring injuries, Allan is never going to be as good as Latrell. Matching that Dogs offer just to play him on the wing would have made little to no sense.
Souths have some decent depth out wide in Paulo, Johnston and potentially one of Burns/Gagai/Graham so letting go of Allan probably doesn't hurt them in the long run.
It does raise a question as to what on earth the Dogs are doing though. Hoppa, DWZ, Allan and Meaney are all capable at FB. No doubt there's abit of flexibility in terms of where those guys can play but with Cotric incoming, Averillo the anointed one and Okunbur returning from an ACL they could be stacked for outside backs. That's before they get JAC too.
I reckon DWZ is on his way out. I am fairly sure he is on a sizable contract and they won't renew it. The other dudes are all expendable. Okunbur could be anything, such an amazing talent but a total space cadet, would not be surprised if he goes the way of a Dave Taylor or Jamal Idris.