If all of your assumptions are true, then of course you are correct. But, I checked some numbers on the Wynn website that might surprise you.
These are the filters Wynn's online selection tool recommends for a 14 inch DC.
35A274BLOLClosed top, MERV 15, Nanofiber filter media, 222 sq ft (open pleat design), 17.5” diameter x 23” tall, outer cage – no inner cage
Notice the the HIGHER efficiency MERV 15 filter has 52 less SQ FT than the lower efficiency MERV 10 filter. So your assumption that HEPA filters will compensate for loss of airflow by adding more surface area may not be correct. Perhaps the manufacture may be motivated to put LESS filter material in a higher efficiency filter to meet a certain price point for the market. Or maybe the filter media is thicker and just can't be crammed in as tightly.Closed top, MERV 10, 80/20 Blend filter media, 274 sq ft, 17.5” diameter x 23” tall, outer cage – no inner cage.
Now the question is for the Wynn MERV 15 filter, is 222 sq ft adequate surface area to maintain air flow on my system? If they would report the CFM capacity per area unit of the filter material I could calculate it. But they do not give that number. I cannot find that number for any pleated filters. For example, I have seen a 1 micron felt bag report 50 CFM capacity per sq ft of material. In that case I can calculate the area of material and multiply by 50.
Keep in mind, I am talking about MY DUST COLLECTOR specifical. In my first video I measured the "free fan" (no filter installed) air flow at 570 CFM. Then with my freshly cleaned felt bag install I measured 566 CFM. So, if all of your assumptions are correct I would stand to gain 4 CFM in increased performance assuming a HEPA cartridge offers ZERO airflow resistance. On the other hand, if the HEPA cartridge introduces more airflow resistance than my felt bag then I stand to loss CFM not gain. Seems like a very poor risk/reward proposition.
Note, also in my first video I tested the air flow when my felt bag was clogged. It was 322 CFM. Thats a 244 CFM drop. This shows how much impact filter clogging can have. Fortunately felt bags are easy to clean with a few seconds of tapping and shaking to recover most of the CFM loss. It is my understanding that the closely packed pleats of a HEPA filter are not as easy to clean and therefore harder to recover the CFM loss due to clogging.