To my knowledge, it still is. It's always been on a space-available basis. The trick is, since the time of the Clintons and the institution of Tricare (replacing "CHAMPUS"), the military treatment facilities give a higher priority to participants in "TRICARE PRIME".
The big difference between now and the old days is that dependents and retirees cannot get dental care (except for emergencies) stateside. I think dependents can still get dental care overseas...not sure about retirees.
I’m 80% and I don’t get dental.