Those are contractions, not possessives. "He is" and "she is", just like "it's" is always a contraction, never a possessive.
You're just proving the point: "'s" is only possessive for a noun. Your examples aren't possessives.
Yes, I misunderstood his point entirely. On reading my response again I also realize that my examples come off as a not so subtle insult, and which is not what I meant.
Those are not possessives. They're contractions, like it's.
Yes, but as a contraction of "he is", not as a possessive.