YUP - I've never shot teflon as I refuse to wipe as you know - but - your hypothesis sounds solid.
I had a similar thing happen with my .69 when using a certain white stiped blue denim that Taylor had. I measured it at .0185" to .019" with the mic, .0215" with my favourite set of calipers. They put 5 consecutive shots on top of each other - a normal 1/2" to 3/4" group on centres at 50 yards using 125gr. of 2F, then open to 4" to 5 in the next 5 shots, the last three of those 5 shots being way out. Picking up the patches told the story.
The last 3 were blown, so I switched back to my normal .030"(calipers) denim .025"by the mic. and every patch was good after that - to the point I shot another 50 shots that day, with the same 10 patches - 6 shots per patch - picking them up, re-lubing and re-using them. Accuracy remained the same wonderful tight groups, from 125gr.2F to 140gr. 2F under an inch at 50 yards and under 2" at 100 meters(109yds.).