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.