In FZA imaging system, the Fresnel zone plate is placed only three millimeters from the sensor. Jiachen and his colleagues took a series of pictures which are displayed on an LCD monitor.

“Optical Fresnel zone plate flat lenses made entirely of colored photoresist through an i-line stepper ”, Light: Science & Applications, DOI: 10.1038/s41377-024-01725-6 ...

Assuming that it's really a free space path with no fresnel zone interference. If the antennas are correctly aligned for maximum gain, then using the theoretical main lobe gain is appropriate.

That announcement brings new salience to a Sony patent for "Fresnel lens and manufacturing method for Fresnel lens" (PDF). The patent was first filed in 2017 and issued by the USPTO in May of 2020 ...