Your observation about dimension of antenna is nearly correct. I am not at home now. When I will reach home, I will measure and post its dimensions.
but just doesn’t look right somehow…
The loading coil (to improve SWR) at the base is missing.
The coil in this antenna is between two sections (1/2 wavelength & 1/4 wavelength) and is a phasing coil. A 1/4 wavelength hairpin shaped stub could also do this job, but is inconvenient due to its physical shape. A coil is commonly used, and the hairpin stub is rarely used.
Please see this post about 1/2 over 1/4 (=3/4):
A 3/4 λ Collinear Groundplane Antenna
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