Unclear requirement on Module Source Objects prototypes

[Ms2ger]

All Module Source Objects should have a prototype of %AbstractModuleSource%.prototype.

Why "should"? Per RFC 2119:

3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
   may exist valid reasons in particular circumstances to ignore a
   particular item, but the full implications must be understood and
   carefully weighed before choosing a different course.

I think it should (pun not intended) either say "must" or clarify when it should be different

[nicolo-ribaudo]

The problem is that users can Object.setPrototypeOf on them, but that doesn't make the less Module Source Objects.

[Ms2ger]

Sure, but I assume this line is meant to require things about the initial situation.

[ljharb]

indeed; they must initially have that prototype; it's fine if it's changed by user code later.

[guybedford]

I added an editorial update in tc39/ecma262@a91247d to change this to "must be initialized" over should.