If you have a non-spanning item, https://drafts.csswg.org/css-grid/#algo-single-span-items

• For min-content maximums:
  If the track has a min-content max track sizing function, set its growth limit to the maximum of the items’ min-content contributions.

But for spanning items, https://drafts.csswg.org/css-grid/#algo-spanning-items

• For intrinsic maximums: Next increase the growth limit of tracks with an intrinsic max track sizing function by distributing extra space as needed to account for these items' minimum contributions. [...]

Why do we distribute the min-content contribution in the former case, but only the minimum contribution in the latter?

.grid { display: grid }
.grid.one { grid-template-columns: minmax(0, min-content) }
.grid.two { grid-template-columns: repeat(2, minmax(0, min-content)) }
.grid > .item { min-width: 0; background: cyan }
.grid.two > .item { grid-column: span 2 }

<div class="grid one">
  <div class="item">Foo</div>
</div>
<div class="grid two">
  <div class="item">Foo</div>
</div>

looks like

Thus violating

Note: This step is a simplification of the steps below for handling spanning items, and should yield the same behavior as running those instructions on items with a span of 1.