well there are plenty of countries who don't celebrate labor day (usa is the only one that does, really) so maybe your question will be answered by a foreigner
anyway, that switch is more about instrument level vs line level. if you were running the vtd in a loop (god forbid!), you might want the boost to bring it to line level. but for general usage, i find that all it does for me is make it harder to set levels, so i leave it off. i figure i never needed it for the original vt and i don't need it now.