@DamkerngT. In the traditional set of case labels, it's nominative vs genitive

Rather than nominative vs possessive

But in this example, I'd suggest it's really accusative vs genitive

You doesn't have distinct nominative and accusative forms

But he/him does, and if we swap that in, we find him

Non-traditional case labels: subjective, objective, possessive

Traditional case labels: nominative, accusative, genitive

They're just labels, and it doesn't really matter which system you use, but it's just a teensy bit weird mixing and matching :-)

In my experience, linguists almost universally use the traditional system

So I do too, just out of habit

I noticed some folks on ELU got a bit bent out of shape on seeing terms like accusative or irrealis

Interestingly, Wikipedia asserts that "most grammarians" now use the non-traditional system, but I've never seen a serious academic publication that did. I think the non-traditional system is often used by language educators, though

I've grown skeptical of "most linguists" and "most grammarians" on Wikipedia

@DamkerngT. I remember upvoting that answer! :-)

I do think it's possible to elaborate on it a little bit.

'Cause is short for because, true. It would help to talk about it's normally spelled with an apostrophe, and how if you leave it out, you might confuse people.

That might not be obvious to learners.

They could also point out that it's not limited to lyrics―it appears in all sorts of informal speech!

It isn't used much in writing, unless you're trying to making your writing resemble informal speech (like in dialogue or informal chat)

And likewise, it isn't used at all in formal speech

So sure, it's a short answer. It's correct and it answers the question.

But there's certainly room to write a long answer.

So I wrote one.

And it got downvoted, interestingly! I can't see any mistakes, though, so unless I'm missing something, the downvoter is wrong.

Well, now we know!

They didn't downvote because they found a mistake. They'd actually rather the answer be only one line

So @DamkerngT., now we have even more support for the idea that an answer can be one line long on ELL!

Not only is it possible―some users prefer it! :-)

@DamkerngT. Well, I was at least a little bit worried there was a factual error I didn't notice

Sometimes it's easier to find other people's errors, harder to find your own

So in a way I'm glad to read their comment, since now I know the downvote didn't signal a problem with the answer :-)

Or objective, if you like. The important thing isn't the label, it's just the distribution of forms: I saw him baking cake, but not *I saw he baking cake.

Well, you and you are awfully similar.