Missing assertion markup in 7.3.2?

[mmccool]

The following sentence in section 7.3.2 is not marked as an assertion:

If the missing feature is to customize existing functionality of an API,
the server will respond with 501 (Not Implemented) HTTP status.

Not being marked as an assertion seems out of place, and the use of "will" sounds like it should be "MUST".

[mmccool]

There is normative content elsewhere in the doc that covers what this says, so this is not an assertion itself. Closing, nothing needs to be changed (although maybe we can clean up the wording in an editorial pass later).