You're absolutely correct.

Roy Lewallen, W7EL

Gene Fuller wrote:
I believe that all three people (Richard, Roy, and Fred) who have
commented on this topic have misread the figure in Kraus. The gain at
one-half wave spacing from the reflector is *zero*, not zero dB
(relative to a dipole), nor zero dBi.

As expected from the simple mirror image model there is complete far
field cancellation in the phi = 0, theta = 0 direction. That is the only
direction referenced in the figure.

73,
Gene
W4SZ