[css-grid] auto minimums under a min/max-content constraint aren't floored at zero #3570

In https://drafts.csswg.org/css-grid/#algo-single-span-items, the base size is always floored at zero:

set its base size to the maximum of the items’ min-content contributions, floored at zero.
set its base size to the maximum of the items’ max-content contributions, floored at zero.
set its base size to the maximum of its items’ minimum contributions, floored at zero.

except in this case:

set the track’s base size to the maximum of its items’ min/max-content contributions, respectively, each limited by the max track sizing function if that is fixed and ultimately floored by its minimum contribution.

Not sure if the flooring is needed (can minimum contributions be negative?), but the inconsistency seems strange. Is it intentional?