Ren, I wouldn't be at all surprised, but as far as I know apart from the low floor versions I don't know if the others are any better for wheelchairs. My take was the fact the door was always open and they thought after about 100 years people may start falling out.
Many boroughs dealt with this in the 70s by adding folding doors 'just in case', and had this been the reason it would have been far better to do that instead of dumping them on the scrapheap. Like the Twin Towers of Wembley which were seen from our back bedroom, sadly missed.
Here's another view of my mum's amazing garden, more of which becomes planted by me as I go along as I share the gardening duties with her professional one.