I self propelled wheel chair wheel has the centre around 110 mm from the floor, that is where it hits a wall, so the idea is to put the sockets out of harms way, pedestrian controlled and electric will have lower points, so around 150 mm gets the socket out of harms way from wheel chairs. Reaching sockets is another point, in a wheel chair around 900 mm is the point where the user has most reach. Side on the user can reach the ground, but in front it is much reduced, for some reason we have 400 mm in most buildings but 450 mm in domestic, in real terms being higher does help when low furniture is in front. As said nothing says what height it must be, in fact you can get sockets in the floor.
Visible is another problem, my mother was in a wheel chair, and to see the heat setting on her oven one needed to look down on them, I had to make new plated so it could be read from below.
The touch controls on the hot plate were the worst, these also designed to be read from above, at the angle of her eyes to display, could not see the controls, had to change hob for one with knobs on.
The idea is if we follow the suggested heights then wheel chair users will have no problems, but I question if the writer actually used a wheel chair, in the main having sockets and the like low is better than high, a tall person can bend down, but a wheel chair user can't jump up.
