Right, you highlight reasons why you can't compare a normal non-
DAS guest's experience to a DAS guest's experience apples-to-apples.
Note, I didn't mention anything about the reported change to add a cool-down timer to the DAS request after tap-in. I think that this helps alleviate your stated concern about the double-line standing. You mention specifically BTMR, which has a second tap-in point, right before the stairway down. The 10 minute cool-down after that second tap-in will likely put you right in the middle of loading, the roller-coaster itself, or even after the ride, depending on how the CM are managing guests on the stairway and the timing of when you arrive to the second tap-in point.
In my experience, this really wasn't much of an issue. Most of the "bigger/E-ticket" attractions have a second tap-in point close to the loading of the vehicle making this mostly a non-issue. In those instances, I found it unwieldy to be trying to manage the group, get loaded up, experience the attraction and get my phone out to try to find the next attraction to request a return time. Most often, I wasn't able to request another time until after exiting the ride vehicle.
This significantly impacts your example. If the DAS user isn't able to book the return time for another 5 or 10 minutes (i.e., until after they've actually ridden), then the experience time is very close, assuming that standby time is spot on. Any variation to that time, or quicker pace to the non-DAS user's gait to Buzz Lightyear's, and the comparison also starts to be a non-issue. I'll note that at "Average" pace, touringplans estimates only a 10 minute walk from BTMR to Buzz Lightyear's. And, this is a pretty extreme example, going from one corner of the park to diagonally across the park.