FindUsersByName

I created a custom membership provider and I have implemented this method ( FindUsersByName). But as I was doing some testing I noticed that FindUsersByName does not always get executed when performing a search. It seems like it a method before it returned 0 results then it calls FindUsersByName. If the method before it returns > 0 results then it does not bother to call FindUsersByName.
 
Does anyone know the method? I want FindUsersByName to execute everytime.
 
Thanks!
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