The documented reasoning and references do not make any sense. Older browsers are going to choke on newer syntax regardless. This is an ongoing issue in the JS domain that is managed reasonably well via e.g. polyfills, tooling and rapid release. Often with code bloat initially, sure, but the browsers catch up. The days of "oldIE" are long gone.

The point of the declaration is to tell the browsers that can handle the syntax to handle it. Another method could be to use a new linking method. Regardless, the language would still gracefully degrade as only the newer syntax would require strict rules in place.

Please explain it to me if I am completely missing the point.