That's okay Charlie, you were just repeating what you heard, which is one of the oldest myths there is to do with speakers. Yes, the typical speaker has a wide variance in it's impedance, and I do mean w-i-d-e ! On some speakers, the impedance varies tremendously in the range we use with pedal stee;. So, your ordinary 8-ohm speaker impedance
actually varies from 6 ohms to something like
30 ohms, depending on the frequency you're feeding into it.
Believe it!