Because it is still a single tier stand.
The break in the stand is for the back of the safe standing. People in the first row of the upper (seated only) section won't have their view impeded by those ahead. (Believe it or not, not everybody behind the goal likes to stand.)
No. They can't, even if they make the upper section safe standing I think it's wide enough for a wheelchair to pass down that gap. (wheelchair bays at that level in all four corner quarters.
The reduced height was due to the clubs miserable cowing to UNESCO and English Heratige. Should have just flicked the Vs at them.
I get it, I'm also disappointed it's not a continual single stand. But I'd rather focus my energies on the continued miserable performance of our chairman and his staff of arse sniffers rather than being worried about a few shy and sensitive lads who are too bashful to start a chant down the front.