I flew for years those fighters with the extended probe (F1, 2000) and also the ones with the retractable device (Jaguar, Super-Etendard)
Regarding drag, as you always have external loads nowadays, it's not such a big deal.
Having the probe permanently and rigidly extended (isn'it ?) means that it would not suffer from an electric or hydraulic failure, and stay inside the body when needed...
