There are different clues in different contexts. The hardest is if there is a very technical definition that makes another answer more correct.

Maybe in a test of English:

"John has less _____ than Mary. So they decided to go to Mary's apartment for breakfast."

A. Bread

B. Window

C. Eggs

D. Times

"

This is an incredibly stupid question oh my God. What would I even pick.

All of the choices, and the whole question, is so stupid.

But anyway obviously they want you to pick "eggs" because you are supposed to know it is good for breakfast. You can tell how low the bar is by its inclusion of window, as though you might not know this simple word.

It is ungrammatical to say "less window than", "less times than" and "less eggs than" (you're supposed to say fewer eggs than.)

Only "bread" is grammatical in that sentence and it makes just as much sense as all the other stupid choices, but I would pick the ungrammatical choice C (it's a hard one though, the resulting sentence is stupid) versus the grammatically correct choice A.

This is just a technical distinction though.

Bread could be slang for Cash which fits grammatically and would also be a reason to go to Mary's apartment for breakfast instead of Denny's.

Less window is informal but I don’t see how it’s incorrect. Bread is both correct and fits the context better.

Yes but from "times" you can see that this is a test of VERY basic English. I agree with you that Bread is both correct and fits the context better, and I would still choose "eggs" (a worse answer, from the choices given) because I would analyze what the (really stupid) question-writer wanted.

You are right that window exists in that sense but in this case it's clear that the question writers didn't think about it.

For "window" in particular, we rarely say it the way you imply, the whole Internet has just 4 instances of these words after each other:

https://www.google.com/search?q=%22had+less+window+than%22

(you can try 'have' and 'has' for 'had'). But you might be right that the informal sense of "window" that I think you imply (window of time) might be technically the best answer in a different context but absolutely not the answer to pick!

So it actually is a good example of a potentially better answer that you shouldn't pick after analyzing the question!

“Less eggs” isn’t actually correct. Eggs are countable, so it would be “fewer eggs”.

You can have “less bread”, or “fewer loaves of bread”.

This is getting very pedantic though.

This is specifically what actually makes it, eggs, objectively wrong -- though it is the choice that will be marked correct and which you, the test-taker should pick, even if you realize it is wrong. Pedantically, it is wrong to say "less eggs" while it is correct to say "less bread" but due to the level of pedantry, you, the test-taker, should prefer to pick the incorrect answer (eggs) over the only actually grammatical answer (bread) - even though this is a test of English.

You have to set aside what is correct and incorrect and decide how educated the test-writer was, and what they might want you to pick, or what they are attempting to test.

This has direct relevance to the article are discussing.

No, I meant less physical window, although I see what you are getting at with the other sense.