Update
I worked with MMM this morning. Standing on the first landing and he on the first step down from me, like Dr. Shelli said and he did come up in fact rather quickly. So we did all three floors (technically 6 flights with landings), making a big "McKinley is a good boy party" at every landing and floor.
The second time we did it, it was so funny (later in the morning).
Now know that landings have no doors into the condos. I stopped at the 1st landing and he came up the one step and THEN went up the whole entire next flight of stairs ALL BY HIMSELF to the floor with doors and tried to go in what would be Amber's apartment if she lived on the second floor.
HOWEVER, when I thought, "well maybe he is over it and started him onto the next landing and the 3rd floor, HUH HUH


. went the little Sheltie face.
So I carried him to the top step set him down and I went up the next step to the landing AND.......... he came up the last step straightaway to the landing and then bolted up to the floor with doors ALL BY HIMSELF again and went immediately to her door.
What goes through their little minds??? How I wish I knew!
And that is where we are at the moment in his getting over the fear of steps. So I guess the good news is that he is going to get over it and my back is going to be spared!