All Gulfstream models prior to the G650 utilized a gust lock mechanism, which from personal experience I can say never once presented a problem. It was always very straight forward, follow the checklist; release the gust lock prior to engine start and do the full flight control checks (Which take all of about 5 - 10 seconds) after engine start.
If you read the full transcript of the NTSB report as well as Gulfstream's report on the testing of it's gust lock system you will see numerous references to the handle mechanism being "worn" or "broken". (Physical evidence from the accident airplane shows that the handle was not in the fully down position and the handles that failed to fully protect in the Gulfstream tests were similarly worn.)
I'd say that Gulfstream is not so much conceding that the mechanism is defective, rather they are giving crews a stern warning, follow the procedures in the AFM and checklists.
Gulfstream's newest model, the G650 doesn't use a gust lock and instead relies on hydraulic damping to prevent control surface damage. Interestingly, years of habit of following the "Before engine start" checklist of the previous models still occasionally causes me to reflexively say "Gust-lock, released".