Do you mean as to wether or not he explained about Sirius Black beign an escaped prisoner or not... I don't really see how it makes a different.. the fact that they can be taught to recognise someone and not allow then entry is kinda the point...
I mean, to continue with the garage door, it can recognise that a person is there, but not a specific person. ie, it can't decifer wether it is you or say your dog, and them, after the recgonition, react differently depending on who it is...
