As I said it is likely and as you said it is logical, but that does not mean that it is prooven. There has been no official statement confirming it (that I have seen) nor any major investigation made (that I have seen).
For those of you that have played HT, you might have seen the mythbusting thread and specifically the clown issue. For many years it was cnsidered a true that "clowns" worked, it was even inludd in the rules (even though it was not refered to as clowns), however I never trusted that, as I could not see any proof of it having an effect (thus I have never had a clown), and now finally it is stated that they actually dont.
For now I will keep using the information as something that is "likely" to be true.