No - they are not saying "treat them as if they are fine". They are saying many people don't need accommodations other than bring able to bring a mobility device in lines/attractions. Having a handicapped parking permit or using a wheelchair doesn't necessarily mean a guest needs more than their mobility device.
Disney's response to guests with "Stamina or Endurance Concerns" who are concerned about their ability to wait in line has always been to suggest a wheelchair or
ECV.
If the person has problems with standing in line or with walking, a wheelchair/ECV, or rollator would give them a place to sit even they need to. A trip to WDW includes a lot more walking than just what you do in line and there will most of the time be no place to sit while in line. The distance walked is not usually less with using
DAS.
Most of the lines where you will actually standing still for long periods are the lines for shows and movies. Because those 'load' large numbers of people at a time, people have to stand waiting for the next show to 'load'. If each show is 14 minutes, you are going to be
somewhere for 14 minutes. In many shows, much of the time in that place will be a preshow area. If you don't have a mobility device, you will generally be standing during that time.
Post 22 on page 2 of the disABILITIES FAQs thread has a list of attractions like that where guests will need to stand.
This is what it says in the DAS information posted on the Disney website:
"The goal of the DAS Card is to accommodate Guests who arent able to wait in a conventional queue environment due to a disability.
A Guest whose disability is based on the necessity to use a wheelchair or scooter does not need a DAS Card.
Depending on the attraction, Guests utilizing a wheelchair or scooter will either wait in the standard queue or receive a return time at the attraction comparable to the current wait time.
If you have additional needs, please discuss them with Guest Relations."
At WDW almost all the lines/attractions are wheelchair accessible through the regular (Mainstream) line. DAS is not required to use a wheelchair or mobility device in lines (it would actually be a violation of the ADA for them to require "proof" in order to bring a wheelchair into attractions). For most people with mobility related issues, being able to use their mobility device in attractions is all they need - those people won't need DAS.
People who have additional needs besides the mobility needs that affect their ability to wait in lines will have to explain those needs.
Since the only accommodation that DAS provides is being able to wait outside of the line, guests with concerns about stairs, distances walked, standing still for periods of time or moving walkways will still not avoid them entirely - they are part of the line (including the Fastpass line) the boarding or part of the attraction.
Guests who need to avoids stairs or have moving walkways slowed will still need to explain their needs, even if they have DAS.
If they have a mobility device, the CM can see that they need to avoid the stairs or whatever. If the guest's mobility need is not visible (such as using a wheelchair, ECV, cane, etc), it doesn't matter whether they are using DAS or not. They will still need to explain what they need.