On page 343 he goes on to comment upon work by Kuhl and Plantz about how people such as recording engineers prefer directional loudspeakers for work, but tend toward less directional ones in their home.
The design criteria from which I took the directivity characteristics of my louspeaker system from come from Kates in the paper,"A perceptual criterion for loudspeaker evaluation", AES Journal Vol.32, No.12, 1984. On page 940 in the section "Floor reflection", he states as you do that a reflection coming from the same direction as the direct sound will have no binuaral echo suppresion, and shows that at typical listening distances will fall in the critical band and, "Thus we would expect floor reflection to be an important cause of colouration".
Your loudspeaker system I note has 90 degree vertical directivity, in which case early vertical reflections will be a definite feature.