We'll agree to disagree on this one. I have never met someone who made the claim that BWV was relatively as close to Epcot as BCV, so this is a first. I have stayed in BCV several times and we are always in the BCV building elevator, literally, within five minutes after walking out of the World Showcase gate. And that's not speed walking, either. That is normal "I've just had 5 cocktails" walking. From the Epcot gate to the "secret" BCV walking path (as my daughters call it) is 2 minutes. From there to the BCV building is usually another 2 minutes if there isn't someone really slow in front of you. I have routinely been on my balcony within 6 minutes after leaving Epcot.
We walked from Epcot to Boardwalk to get a slice of pizza in February and it definitely was longer. We opted to just wait for the boat back to BCV because we were tired (it was late) and that walk was daunting at the time. You are correct with your 20 minutes estimation for going from BWV to Epcot, but that is 4x longer than the walk to BCV that I just described. So, yes, 20 minutes in the big scheme of things isn't long...but when you are tired at the end of the night another 15 minutes feels like forever.