How does the distance between two antenna count in Friis Equation?
A Friis reflective path null occurs when the incident and reflected signal are both, but one is delayed by any multiple of 1/2 wavelength such that they cancel out.
Your hypothetical problem shows one line of sight path of TX antenna to the fringe side of Rx antenna. This ground fringes are more likely to equal and cancel line of sight path fringe loss than skyward reflections.
With an irregular shape antenna that is likely to have many irregular null lobes, unless you know that your Line of sight path is on a good side lobe, you can expect poor reception as well as motion Rayleigh loss and static Friis loss.
An accurate analysis requires and accurate antenna gain phase dispersion plot.