Think you might be right:
I've worked with F-18A/B/C/D/E aircraft for over 17 years. There has not been a flight clearance for the AIM-120 on the wingtip stations. The F-18A-D will only fly with a LAU-7 launcher on the wingtips which will only accomidate varients of the AIM-9 missile. The F-18E/F has a LAU-127 launcher loaded on the wingtips. It can carry both AIM-9 and AIM-120 missiles. However, there is only flight clearance for the AIM-9 currently. Nothing in the works at present for the AIM-120. I agree, 120 loaded on wingtip will put enormous stress on the wingfold transmissions as well as the mounting hardware for the launcher itself.
http://combatace.com/topic/48322-aim-120-on-hornet-wingtips/