Agreed. I'm kind of surprised that Leo ever let that shortcoming slip through his otherwise genius designs (although many of the pre-CBS Fender bass necks I've seen sat high enough in the pocket where you could adjust them with a screwdriver if you were willing to dig into that little notch in the pickguard a bit). The truss rod access notch with the T-Bar tool that Fender employs on their (1995 to now) American Standard P and J basses is one of the best truss rod systems out there (along with the Ernie Ball Music Man truss rod "wheel" system), IMHO. Having to take the neck off to adjust the truss rod makes a relatively straight forward maintenance activity a real pain in the arse. * It also can lead to stripped neck mounting holes, chipped finish in and around the neck pocket in the case of a tight neck/neck pocket fit and frayed string wrappings if the neck has to be removed and reinstalled too many times (particularly by a cheapskate, hack, knows almost enough to be dangerous DIY repair guy like me). My American Standard P necks have been pretty darn stable for me, but on the rare occasions that they do need a tweak, that T-Bar tool can do the finest of adjustments with no muss & no fuss. I've been known to file a truss rod access slot on my own Fender bodies & pickguards when the neck sits high enough in the pocket where I can do DIY it with a simple circular file but have also have had a pro do it for me when a substantial slot was required that was beyond my meager skill level and tool ownership.
* I have a bass buddy (who's actually a pretty skilled luthier) who considers removing the neck to adjust the truss rod some kind of "manly" right of passage thing to do and has been known to tease me about routing truss rod access slots in my basses. Life can be a struggle ... I'll take "easy peasy lemon squeezy" any time I can get it. ;^)