BOMA and ANSI standards while calculating the STAIR

Hello .
I have a question about the stair calculation.
I have a 3 level Towhouse and my co worker exclude the stair and in my opinion in should be included . Please see the attached. My question is the green area included in the lower floor square footage?

From my understanding when I read the ANSI Z765-2020 page 5 and diagram on pages 6, 7,8
Stairs: Runs/treads and landings both count in square footage totals. They are measured as a part of the floor “from which they descend,” so are generally counted twice in a typical two-story home with a basement

As quoted on page 5:

" Finished stairs suitable for year-round use ascending to an unfinished upper area are included in the square footage calculation. In addition, areas beneath stairs are included in the finished square footage regardless of the distance between the stairs and the floor below or of the degree of finish of that area."

I also include a sample of 4 level house from iguide that uses code ANSI Z765 2021 and they calculate the stair twice. Please see the floor plan on this link .iGUIDE 3D Tour for 135 E 63rd Ave, Vancouver, BC

Please let me know your thoughts on this topic.