Worked for a large manufacturer. The truss is a big part of it. There’s no benefit to loosening strings for storage. If there was, manufacturers would do it. If there was, guitar techs would do it.Wood will react to whatever stresses are put on it - both internal and eternal. Adding an external stress does not stabilize a neck - it makes it more likely to move, not less. If a piece of wood (or a glue up of multiple pieces) moves over time on its own (without external forces), it means internal stresses are being relieved (the wood wasn't stable when you got it). Adding an external force does not help that - wood that wants to warp will warp.
I've stored necks for years with no tension on them from strings or the truss rod, and they come out straight. A well set up neck always has some bend (more than if it has no tension on it) because we want some relief. I've taken to storing basses I'm not playing for a while tuned a whole step down, which works out to about 25% less tension. The reduces the relief a few thousandths. Not sure if that will have a big advantage over time or not. So far, it's working fine.
In a perfect world it won’t help or harm.