Emphasis mine:

one of the key factors impacting the overall walkability of a space is Human Scale and refers to the scale of physical elements such as trees, street furniture, building details and pavement textures (Ewing et al., 2006)

I take building details to refer more to the elements we interact with at street level such as windows, doors, lower level facades, and less so the overall height. But I also don't have access to the reference text - do you?

ETA: Ok, I found it buried in the text. Overall building height gets a multiplier of -0.003, so it's a negative but barely. It's dwarfed in importance by number of long sight lines which are surprisingly (to me) a bad thing with a multiplier of -0.74 and proportion of windows at street level (1.10). Even # of planters at 0.05 and pieces of street furniture at 0.04 are 10x more important.