The counter clerk at my local post office decided it was mistaken so she didn't charge me. She did make a point of telling me to make sure that when I mail bubble wrap envelopes to put some kleenex or similar in the envelope to make sure it is thick enough to be charged the lower rate.

One other thing she told me was that the "word on the streets" at the post office was that USPS will be coming out with some clarifying regulations next year because of all the confusion surrounding the present ones.

Cheers!
Bill