No one from this board has reported riding yet with a wheelchair, so I can't give you an exact answer. I can tell you how it was before the renovation and speculate on how it probably is now.
Here's how it was:
After being assigned to a starship, the guests waited in lines - one line for each row and the correct number of guests for the seats in that row. Sort of similar in ways to Mission Space or Soarin'.
The seat closest to the entry door in the first row of each starship was the designated wheelchair user spot. So, the wheelchair user waited in the last spot in the front row and followed the other guests as the walked in to take their seats.
There was enough space between the first row and the front of tbe 'cabin' for a wheelchair to be parked very close to the ride seat for transfer and to drive thru to the other side of the cabin to exit.
I don't remember if the seat had a swing away armrest - like an airplane seat - for transfer or not, but I think it did. I know that there was a regular seat belt and guests in that seat could also request a 5 point harness if they needed more trunk support. That was stored by that seat and the seat had attachment points where the harness fastened in. After the guest using a wheelchair was seated, a CM took the wheelchair away. It was brought back after the ride was complete.
The non motion option was called a 'training run' and was running the ride car with just the movie and no motion. It was not always available because it meant taking one ship out of commission. I don't know if it was difficult or time consuming to change over, but I know many people posted that when they asked for a non-motion option, they were given a time to come back for their ride. We never did that option, but as far as I know, the person still had to transfer because a wheelchair parked on front of the first row would be very close to the show area.
My speculation is that this is probably still all the same after renovation.
One reason is that it worked well a large number of people, even those like my youngest DD, who needed to be lifted from her wheelchair and placed into the ride seat.
Another reason is that since the ride was very turbulent, it would be important that the wheelchair be secured very well - better than the tiedown for the Safari or any other attraction. I can't see that they would be able to assure that every wheelchair coming into the attraction could be adequately tied down. If the ride seat actually collapsed somehow, there would be quite limited space for that to happen and still secure a wheelchair in that space.
So, until we have a first hand account from someone using the wheelchair access, I would assume the tweet meant that the arm of the chair swung away, probably to the back. This could easily be described by an observer as 'collapsing'. I would also assume that the word transfer meant the guest transferred to the ride seat. Transfer would be a strange word to choose if the person actually stayed in the wheelchair - it would make more sense to say they parked the wheelchair in the spot.
