I did the last time, but that was to get some padding between the roundwound strings and the fretless pau ferro fingerboard, since the bass might end up laying face-down for long periods.
But yeah normally I'd agree with the above wisdom, that string tension is probably better than none, unless you loosen the truss rod too. But if I received a bass in the post with the truss rod all slack I'd be a bit grumpy about it.