Hi, I have a theory question about this

So, in the key of Am, the notes are the same as in the key of C - sharps and flats out the window. So playing the A minor pentatonic, I thought that notes that could sound good with it would be the other ones in the key of Am? So adding the B on the first string seems legit, but adding the F# on the second string should NOT sound good, right? After all F# is from the A major scale. And adding F should be okay, right? Well, news : F# sounds good, F doesn't. Also, we add the "blue note", the tritone, and it sounds good as well - very good actually, even so it's a half step away from two notes of the scale.
Is there a way to understand this, or should I just take it as a try and accept it?
Thanks ahead!