They still have to eat but I find at this time I have more success with the mating calls on the fox pro.
It took me a few months to get used to using the Fox Pro opposed to a whistle.
You say that you have Foxes or Cats coming to the same hide after using the Fox Pro, Maybe they are coming from a long distance and it just happens that the Fox Pro got them coming and they make it to where you can see them after that 15 or 20 Mins ?
Also for example there is no use using say a Rabbit or Hare call when there are no Hares or Rabbits on the property...
I have had Great luck with all the calls you mentioned.
Hope some of this helps.