I think it's quite a bit more than a "perhaps". The order is clearly an attempt to target a politically disfavored age bracket; it would never occur to someone without specific animus against CU-Boulder students to write such a narrow rule.
Yes, we should.
> increase mortality by requiring proportionally more at-risk people to get sick to reach herd immunity.
This assumes that herd immunity is reached without a vaccine; the whole idea of controlling the spread is to reduce the degree to which herd immunity depends on people getting infected.