You may well be right that it makes a difference where the fermentation occurs. While I’ve had gut problems all my life going back 6 decades its only now that information is becoming available to us.
I’ve been on a low fermentation diet for the last 6 years or so, only adding fermentable starches in the last month when that diet became unstable for me.
I used to get good results from being 80% paleo, then 90%, then 95%. Now I have to be 100% to get lesser results than I used to get so its time for me to explore other things.
My rosacea is now only occasional. I have to keep sugars and ordinary carbs right down. Adding the potato starch hasn’t triggered it. One of the docs I’ve corresponded with over the years reckons he gets the best results for rosacea when he treats the gut for fungal infections.