So upon further research that was a comment by an agent about the standard practice of measuring (according to one guy a who's likely retired by now) It was not in a letter but in reference to a letter.
So I looked more for clarification https://www.atf.gov/firearms/docs/at...ter-2/download
Page 8 lists a specific example for a folding stock measuring and the aol includes the stock as they say if the folding stock is removed it would not meet the 26" minimum
Another specific example cited by many is the uzi equipped with a 16" barrel and a folding stock is sold commercially and has an aol of 24" folded and able to fire.
Hopefully that makes it clear and sorry for muddying the thread
Thanks for that link. I think it confirms that I should be okay. But it sucks sweating such stupid stuff.