I did it a little differently, by cheating.
I tried to loop cut the ramp.
It was stopped at the top, would not go along the flat at the top of the ramp.
So I undid the removal of the duplicate edge that I only did as the lecture had ‘tidied up’.
Now my loop cuts went all round!
Made two on the center line as in previous lectures, moved one left one right by a numerical + and -
Extruded up, with global Z just the railings. chose a height, click all done!