Of course (and someone correct me if I'm off here), quartz tuners are so accurate that it shows you're off a few cents day to day is only a fraction of a 1/2 step, so you're dealing in a very small amount of drift out of dead-on-the-money.
I've also found that making a bass stay in tune is a combination of the relative stiffness / hardness of the woods involved, properly cut nut- and bridge-slots, the keys themselves, how the strings were put on those keys, a lot of little steps that can add up to how well THIS bass stays in tune relative to THAT bass. These things are easier to see after and understand if you understand how to set up your bass, the whole process.
The advantage to carbon fibre is that it's utterly repeatable in strength, hardness, and whatever tone it adds, or to some people, how utterly transparent with no tone. That hardness is the real key: As others have noted, they found the same thing I heard the first time I played one of the original Steinbergers, the tone is the same at any fretted spot up and down the neck. One of Ned's ideas was that where his carbon blend became resonant to the bass' frequencies was way above the audible range: That self-induced resonance is why so many wood-necked basses can have that 'dead spot' just below the octave on a lot of basses. Alembic sought to do the same with wood by having the many laminations of different woods with their ebony fingerboard scatter this same phenomenon to minimize it. A very hard neck really becomes a factor with fives or sixes with that low B: In my experience, the harder and stiffer the neck, the better the B-string becomes more articulate.
But then, carbon fiber necks can have their own unique problems. Not all of them have truss rods, and the baked-in, permanent relief may not suit every user, and on some, replacing frets can be a headache. And for me, they just feel unwelcoming, I miss whatever I perceive as that 'wood feeling'. But that's me.
I've never owned a bass with real tuning problems. I'm very fussy about that, and learned what I need to do to make them do what I want. I worked in a music store for several years, and invariably, almost every recently purchased guitar or bass that came back with tuning problems almost always had owner-induced problems that could be fixed with a little schooling and new strings.
It's just another choice that's available, and you'd have to decide if it's right for you.
But there's a difference between a bass with serious mechanical or structural problems that affect tuning (which is fairly rare) and the typical axe that will creep a little sharp or flat, which to me is normal.
