Ability: Eyes of the Runekeeper

On p.111 of the PHB, there is an Eldritch Invocation called the Eyes of the Runekeeper. The rules define this as "You can read all languages". So what makes this ability different than the Comprehend Languages spell (PHB, p.224)?

Comprehend Languages gives a literal understanding of language - both spoken and written. It doesn't extend to hidden meanings, secret messages, cultural references, code, jargon, etc.

Eyes of the Runekeeper gives more insight into what is being read. It doesn't apply to spoken languages. The ability doesn't convey full knowledge, if context is missing. It conveys the general gist of the subject matter. If the person has the context however, a great deal can be learned. It is also possible to gain some of this context by study and reading multiple works on the same subject.