It is very clear, but since you want to be pedantic:
every van I am aware of has
1 driver's side front (driver's) door
1 Passenger side front (passenger) door
1 Passenger side rear door, which may consist of 1 large sliding door, or 2 barn style swinging doors for 3 total openings on the sides of the van, not counting the rear entry, that are commonly used for passenger access
1 rear opening, with either a hatch, 1 side swing door, or 2 barn style doors, which are not commonly used for passenger access
This has been the default van style since the Auto industry started building vans
Some vans also have 1 additional Drivers side door behind the driver's door, which in every case I have seen is a slider, that is commonly used for passenger access
It was only after the creation of this body style, with rear door on each side, that the term"4 door van' came into being.
The concept didn't exist in common parlance untill the extra opening was added
The rear cargo access is still not counted, probably because it's not where normal people would get in the van to ride in it
anyone aware of vans before ,say, the 2000s very clearly remembers Dodge hyping the 'first 4 door van'
It is VERY common knowledge that a 4 door van has 4 doors not counting the very rear door
Just because there are currently, yes, I said currently, a small number of 'flat earthers' still existing, doesn't mean that the fact that the earth is round isn't common knowledge, any more than the existence of a few folks on a website who don't know or believe that a van with 4 doors other that the very rear doors is a 4 door
and yes, you are trying to refute that the people who do know this know what they're talking about
so here you go
From wikipedia
With Generation III, the Chrysler minivans were available in long- and short– wheelbase models; three- and four-door configurations; and eight different powertrains, including electric and compressed natural gas; on a single, flexible platform.
and the article
https://en.wikipedia.org/wiki/Dodge_Caravan
Now, about your statement that the explanation is unclear, I believe that has been well addressed, and I have provided at least 2 sources that back it up
You have provided nothing to show otherwise except "Well, there's these six posts in a thread on a forum"
Hardly proof that a majority of people don't know that a van with a rear side door behind the passenger door is a 4 door
So, where are the vast hordes of people who don't know that a car or van with 4 passenger access points isn't, you know, a four door?
Please find more than 6 people to support your argument, as I know entire dealerships full of people who do know that a van with 4
passenger access points is a 4 door, and an Automotive Manufacturing Company that invented the term, all of whom say that a van with 4 access points designed to give passengers access to seating is, indeed, a 4 door van
Do you refer to a house with French doors as a 3 door house? or does it still have a front door and a back door? Do you count the garage?
and if it's a 3 door, does that mean it has 2 front yards? do tell
When you can provide 1000's of people who don't accede this point, I may accept that it is indeed not common knowledge, untill then the burden of proof is on you