It's also because each neck is unique. Going by what club members have posted over the years, it seems that most Alembics have very stable necks, which makes sense because they are all multi-laminate and because of the craftsmanship. And yes, usually seasonal adjustments are all that are needed. However, the universe felt that I needed a bass that would need constant truss rod adjustments, probably because the universe thought it would help me to pay closer attention to what I'm doing.

My recollection is that the neck on the '78 that I had was very stable. Of course my ability to recollect anything is somewhat less than stable.
But yes; perhaps the bass that needs a new truss rod was affected by a big environmental change. I hope it gets a good home. Love the look of those pickups.