CSS variables in media queries: clarification?

Created by: smlombardi

The 4.1 docs currently say

While we include breakpoints in our CSS variables, they unfortunately cannot be used in media queries.

What, exactly, does that mean? The "they" is ambiguous. Do you mean you can't use variables as media queries, as in

@media (min-width(var(--breakpoint-sm))) {
  .content-secondary {
    display: block;
  }
}

or is it the combination that won't work:

@media (min-width(var(--breakpoint-sm))) {
  .some-class {
    color: var(--primary);
  }
}

or that you can't use a variable in a standard media query, as in

@include media-breakpoint-up(sm) {
  .some-class {
    color: var(--primary);
  }
}

Big difference to me.