There are a lot of falcon purists that don't support the cross breeding that was done - they consider it a pollution of the original North American falcon genes (the Anatum)
I have to wonder if they would have been happier to have "pure" genetics in the only anatums left in the natural history museum along side the passenger pigeon.
As I understand it there were so few anatums left there would have been far too much close relative interbreeding to restore a healthy population. I believe most captive bred birds were from a very few ancestors. And we can see that the anatum traits are still strong. Time will tell if it becomes more prevalent.
Now the cross breeding between peregrines & gyrfalcons is another issue altogether...