So the issue with aircraft like the F-16 is the rapid onset of G Forces. You can snatch on the G’s and go from being totally awake to immdediately nap time with no greying out. The oxygen in your braincells buys you that first six to eight seconds. Lower performance aircraft allow for a greying period as a warning.
I think the rapid onset of G is the biggest thing. A co-worker who is a former F-16 pilot told me that the highest number of G-LOC incidents happened in the T-37. T-37? It’s because it can rack up the G forces very fast even though it doesn’t pull high Gs.