OP, you may find these resources from the US Department of Transportation helpful:
https://www.transportation.gov/airconsumer/preboarding-notice-final and
https://www.transportation.gov/sites/dot.gov/files/docs/Preboarding Notice Final_0.pdf and
https://www.transportation.gov/individuals/aviation-consumer-protection/traveling-disability
From the PDF in particular note (bold added for emphasis):
In the revised final rule published on May 13, 2008, the Department expanded the preboarding
requirement to cover not only people who need a specific seat assignment or who need to stow
their personal folding wheelchairs, but also to cover passengers that “need additional time or
assistance to board, stow accessibility equipment, or be seated.”
For a passenger to be entitled to
preboarding, that passenger must self-identify at the gate as being a person with a disability that
needs to preboard for one of the above-listed reasons. In the section-by-section analysis of the
preamble to the final rule, the Department noted that the obligation to preboard passengers with
disabilities “exists regardless of the carriers’ preboarding policies for other persons (e.g., families
with small children).”
Once I am seated at the gate area, I pay attention to the counter area for that gate [we usually get to the gate before the gate is staffed]. Once the airline staff arrive to start working the flight and appear to have logged into their computers and settled, I go over to the desk and tell them who I am, that I am on that flight and that I will need to preboard due to a disability because it will take me more time to board and be seated. I ask if I need to sit anywhere in particular while waiting. I ask how I will know it is time to pre-board and when they expect pre-boarding to start. I do not tell them the specific disabilities as they don't need to know. Often they will ask if I need assistance with boarding and I will tell them no, I am ok on my own, it just takes more time. Sometimes they will ask me to sit in specific seats in the waiting area, other times they don't. Sometimes they will say they will come and get me to pre-board but usually they just say there will be an announcement when pre-boarding starts. I always try to sit facing the gate and desk so I can see when they are getting ready for preboarding.
SW