Read the rules. I will write them for you here.
Open-topped vehicles do not have specific fire points. Instead, all passengers in an open topped vehicle may fire, measuring range and line of sight from the hull of the vehicle. Open topped vehicles do not have specific access points. Models can embark or disembark within 2" of any part of the vehicle.
At no point does the section of open topped rules state embarkation/disembarkation are from the HULL. Specific word. OR define what the hull is. So again. Someones typed something claiming that is what it says, doesn't quote the book, which I have, and from what I can see is writing down the rules how he believes it works.
The part refering to the HULL is to do with passengers shooting from the vehicle.
By the rules stated, which I have underlined as well as emboldened, they can disembark from 2" of ANY PART OF THE VEHICLE.
Again, don't hate me, playing devils advocate, but just trying to show how RAW do not clear this problem up, if anything it points the other direction.
I think you need to read all the rules, and I mean everything that applies not just pieces parts. Parsing them like you and others have trying to prove a point without using all is cheating at worse and rules lawyering at best.
Read the rules on open topped, on open toped says the firing points and acess points are the whole perimiter of the vehicles hull. You then have to read the vehicle rules where it refers to how to measure to and from a vehicle and what the "hull" is by the rules. THis also applies to how you measure for diembarking but you need to read those rules as well since it references access points which you then have to know what that means in relation to open topped. Trying to use a "2" from any part of the vehicle" quote fails when you apply the rest of the rules that also apply and define the vehicle. See I've read the rules multiple times myself and they're rather clear if you don't try to read into them and realize some parts greatly change other depending upon situation and timing.
Have you read all the rules now? Like where it says you ignore things like dozers, decorative bits, wings, etc when measuring? That's in the basic vehicle rules on measuring.
The hull is the base body of the vehicle is it not? Again that is in the base vehicle rule.
So a door, being as it's not the base body of the vehicle and is for all intents and purposes decorative since if it's closed you can still use it as an access point or firing point then is must not count for measuring or any other things that entails measuments if modeled in some other position.
Do you measure from the ramp or the opening at the front of a LR? Do you measure from the ramp or the hole in the rear of a Rhino? Do you mneasure from a modeled open door on the side of a Rhino or LR or do you use the opening in the hull? The answer to all of those is you use the hole by the rules isn't it? So why would a drop pod be different? It's not unless you're trying for some perceived advantage that the rules don't allow. So a pod with doors open mearure from the perimeter of the pentagonal base since be definition that is the best place by the rules you would use to measure same thing applies to having doors closed you use the pentagonal perimeter just the same to measure from
I'm not hating on you, to be honest when 5th ed hit and I actually got some pods I initially thought the way you and other have proposed, but being that SM vehicles haven't counted as open topped for a while I sat and read all the rules that apply and quickly found that what I initialy wanted to believed and what was correct were different. How people want things to be and how they actually are come down to knowing ALL the pertinent rules and how they interact not taking using only the parts that give you what you want.