So maybe a little lift shouldn't be called a warp. I recently saw a SW with a little lift sell at a rather high price which makes no sense if we are that anal about warp. I know that a little lift can be straightened in a butt or shaft so I don't see it being a big deal.
I think we need a consensus on a grading system for lift. Should be able to come up with a real standard we can use in general like they do for inclusions in gems. Just spitballing here using common items to measure, I've heard some of this before but not yet a dedicated grading system.
E-W-extreme warp. Tip, joint or bumper end come off table.
W-warp. Any lift beyond a nickel 2mm+ thickness gap.
H-L-high lift, ends stay on table at a nickel 2mm thickness gap.
M-L medium lift, ends stay on table at a dime 1.3mm thickness gap.
S-L Slight lift, ends on table at 8 dollar bills .9mm thickness gap.
VS-L very slight lift, ends stay on table at a 4 dollar bills .5mm thickness gap.
VVS-L very very slight lift, ends stay on table at 2 dollar bills .25mm thickness gap.
N-L no lift. Less than a dollar .1mm gap.