a few minutes ago I sent the following mail to an OM who asked the same question:
Your thoughts are correct!
The radiator and the reflector disc have a mechanical and thus also an electrical connection. At 2.4 GHz, of course, it looks different. Just think of a loop dipole, where you also measure a short circuit at the (symmetrical) feed-in point. ...And it gets even worse! If the loop dipole is directly attached to the boom at its point of symmetry (which is indeed permissible), there is also a conductive connection to the boom. ... and still the structure works. That is the "exciting" thing about HF technology!
I wish you much success and lots of fun with your activities over QO-100!
73! Peter, DJ7GP
PS .: If you have any questions, do not hesitate to contact me!