I did a test search for a points booking on Chase:



The (E) won't mean anything to infrequent travelers.

If you click to reveal the Rules and Policies, they are very bland and generic, not even airline-specific (e.g. includes mention of risk-free cancellation but says only certain airlines permit it inside 7 days etc.) and do not mention the Basic Economy restrictions.

However when I click Select, you get this pop-up:



So presumably they blew past this without reading it carefully.

OP has already acknowleged this as a learning experience, so I think it's still useful to separate out "it's their own fault so let them burn in hell" from "it's their own fault but here's some things they can try" (which some people have offered suggestions).