Stayed in the park about 45 minutes after the fireworks so there would be no crowd at the bus stop. the regular line was minimal (maybe 20 people) but there were already 6 scooters/ wheelchairs waiting to board.
Something similar to that happened to me too.
One time I left MK and EPCOT early to beat the crowd and there was more than two mobility
scooter waiting in line to go back to Pop Century resort. Another time I was the only one there with a mobility scooter.
Another time I left late after the MK fireworks and EPCOT Illuminations and there were a lot of mobility scooters sometimes and none another time.
I usually like to stay later and let the crowd thin out to watch the kiss goodnight at MK and to let the crowd thin out at EPCOT because of the bottleneck crowds near the large fountain when exiting.
I usually like to go to WDW in December and it gets crowded at times.
As far as Disney cast members calling for another bus, I have seen this happen a few times but it was a few years ago.
I used to see cast members with a tablet at Animal Kingdom Lodge or Pop Century Resort.
A couple of times I saw a supervisory type person at MK calling presumably for extra buses.
I don't know for sure that is what they were doing, but that is the impression that I go.
I know that I am going to be waiting since I use a wheelchair and I accept that.
I know that sometimes there will be other wheelchairs and mobility scooters waiting before me and I am okay with that too.
I remember not feeling like that and being upset.
I am on vacation and I try not to let things like that bother me.
But that is just me.