A special derogation was given to the 466s which allowed them to work alone on the Bromley North line, so I'm not sure why a 465 was used.
My understanding was it was granted for a year, so expired in Dec 2020. When I last used the branch in August 2020 it was a 466, but passing through Grove Park more recenlty I've seen a 465 in the platform for the branch.
I believe there were problems with DOO operation for anything longer than a 2 car unit that led to 466s getting the one year derogation while the issue was sorted out, as literally no other passenger rolling stock was allowed to operate on the line.
I don't think the 466s have had their Persons of Reduced Mobility modifications done so they can no longer work on their lonesome - they have to be coupled to one or more 465s.
They had some changes made, including door buttons + sounds and changing the handles/handrails, but I can't recall anything else being done, presumably because fitting a new toilet and/or disabled seating area would have cost more time, money and physical space than was worth getting back just to keep single unit operations going.