I obviously can’t speak about runDisney, but when I volunteer for races here, there is sometimes a disconnect between what is in the race guide, what is told to the volunteers by the race organizers, and what is either heard or carried out by the volunteers. I always insist that someone show me their id, along with the bib confirmation (either paper or electronic); that is what I am told to do so that is what I do. When people are unhappy about it, I very nicely bring them to staff of the race organizers so they can take the responsibility of making an exception.
I recently volunteered for a race where they had us download an app to read the QR code on the bib pick up confirmation - made it so much easier, particularly as more and more people would show up with only an electronic confirmation - so you either had to remember the number as you looked for their bib or had to take their phone with you (which understandably people didn‘t like for you to do). With the app, not only did it give you all the necessary information (name of racer and bib number) but it also linked back to the organizer’s race registration database so they always had an accurate count of how many bibs had been picked up etc, which helped them with race logistics as well.
And thanks to COVID we had didn’t have any of this « I don‘t have an ID on me » that we used to get - they had to show proof of vaccination or negative test, which is only valid with an ID. People have gotten really good at either carrying their ID or carrying a picture of their ID