oh for sure, that is what my 6 string with a 170 F# has a walnut body. i can feel the b in the aldre body of my 5. but also remember the headstock will amplify the vibrations as it is at the furthest point. the pickups are near the centre of mass and flex would be quite limited.When a bass string is plucked, it's not just the string that moves. An interesting experiment is to lightly rest fingers from your non-plucking hand on the tip of the headstock (or other places on your bass) as you pluck a string. When I do that, I can feel the wood vibrating, and it's different in character from bass to bass. Now the vibrating wood on a solid body bass doesn't produce a lot of sound acoustically, but if the wood is vibrating, the pickups, being screwed into the wood, are also moving in concert with the wood. Subtle to be sure, but I think still an important component of a bass's sound.
but we agree on the concept. i can feel it. but i bet if we did an experiment where a bass was strapped down for zero body or neck flex, there would be little change for what the pickup “sees”. again, i think with sufficient rigidity, the air bass would be pretty darn close.
said in other words, pickups sense left and right signals over the pickup poles from strinng vibration, but they are also sensing other planes of oscillation in the string, some contributed by body/neck flex. thus the sustain we see in neckthroughs vs bolt on.
but until someone does it, it is all “intellectual masturbation.”. i like my bases as they are so i dont get too fussed either way.