[bluGill]

That is trivia that is useless in almost all contexts. I've been a native English speaker all my life and this is the first I've heard of that. I can't think of any situation in life where knowing that fact would have been helpful. Your claim seems reasonable, but if someone says you are wrong I wouldn't fact check it even if clear links were posted so that I could.

[devilbunny]

If you’re seeing a word for the first time, it is pretty useful - partly with pronunciation but definitely with meaning.

You do have to have some familiarity with the source languages, but if it’s an unfamiliar but nativized word, those are almost always ultimately Latin or Greek.

[int_19h]

If you're seeing the word for the first time and need to figure out how to pronounce it, how would you know that “y” is acting as a vowel and not as a consonant in the first place?

[devilbunny]

If it's followed by a vowel, it's likely a Germanic word: yule, your, young, yellow (and you probably know the word, since our core vocabulary is still mostly Germanic). If it's at the end or between consonants, like syllabary or ontogeny, probably Greek.

You might also just happen to know a smattering (or even a lot) of Greek and Latin.

[mousethatroared]

Im a materials scientist and I use etymology every day.

Knowing etymology is a an easy way to memorize things.

[throaway955]

But if you had known it (aka, if anyone had taught it to you), it wouldn't be useless, as you would know the context and how to pronounce it...not to mention the meaning behind it