This paragraph is from a grammar book. However, I know that colons should not be used with "such as".
Is this an exception to the rule that I knew?
Sentences that begin with words that indicates portions, such as: percent, fraction, part, majority, some, all, none, remainder, etc., look at the noun of the prepositional phrase (object of the preposition) in order to determine whether or not to use a singular or plural verb.
To me, that looks like a very incorrect use of the colon. What precedes the colon needs to be a complete sentence (according to some authoritative sources) and, in this case, it is not.
Even if the sentence before the colon is complete, the use of a colon is unnecessary when it is preceded by "such as", "including", or "for example". These phrases already tell the reader that a list follows. See Colons.
The Chicago Manual of Style (CMoS) guide says "... a colon is not normally used after namely, for example, and similar expressions; these are usually followed by a comma instead".
Many writers assume—wrongly—that a colon is always needed before a series or a list. In fact, if a colon intervenes in what would otherwise constitute a grammatical sentence . . . there is a good chance it is being used inappropriately. A colon, for example, should not be used before a series that serves as the object of a verb. When in doubt, apply this test: to merit a colon, the words that introduce a series or list must themselves constitute a grammatically complete sentence. - CMoS
"Do not use a colon (:) after one of these terms ["such as" and "including"]; they are meant to directly introduce the relevant examples." - Editing Tip: 'Such As' and 'Including'.
Also, we don't use "etc." with "such as" or "for example". See this question in ELU.
Is it correct that “etc.” can not be used together in a sentence with “for example” and “such as”?
"And never use etc. at the end of a series that begins with "for example", "e.g.", "including", "such as", and the like, because these terms make "etc." redundant: they already imply that the writer could offer other examples." - All About etc.
