[barrell]

Not really. Fluency is probably closer to 70-95% comprehension, combined with an ability to assume the rest. I assume the comment is talking about native level comprehension, which is still only like 99.99%

Source: native English speaker in Europe. I have to explain/reword several words/expressions per day to people who would be by all means considered fluent.

(all numbers in this comment were estimated based on experience)

[Throaway1982]

I wouldn't consider anyone "fluent" who has only 70% comprehension. More like 90%+. If you're assuming things based on context that is a marker of a low level of comprehension.

Im also a native English speaker and have to explain English words daily to other native English speakers. Dont really think that matters. Some words are more common than others.

[barrell]

I would say "full comprehension" would mean you don't need words and phrases explained to you on a daily basis.

And to each their own. Fluency is a bad metric because it means something different to everyone. If you live in a language, work in a language, and have friends in a language, most people would consider that fluent. I've met many, many people who qualify with a much lower comprehension level than 90%.

Also, speaking from experience, I'll often "comprehend a sentence 100% in another language". Then I'll really listen to it again and realize I'm not really sure about half of the words. I have a vague idea of most of them and in context my brain get's it and self-reports full comprehension.

I think "full comprehension" is a substantially higher bar than "fluency".