PhantomData confusing documentation

Location

https://doc.rust-lang.org/std/marker/struct.PhantomData.html#ownership-and-the-drop-check, via https://github.com/rust-lang/rust/blob/21e6de7eb64c09102de3f100420a09edc1a2a8d7/library/core/src/marker.rs#L728

Summary

https://github.com/rust-lang/rust/pull/103413 updated the documentation for PhantomData to say

Currently, adding a field of type PhantomData<T> indicates that your type owns data of type T in very rare circumstances.

I don't understand. How rare must these circumstances be for me to use PhantomData? What should I do if my type always owns data of type T?

I guess this is not what was meant, but I am finding it hard to figure out what the intention was and propose an improvement.

Possibly just remove the phrase "in very rare circumstances"?

Start with the Ownership and the drop check section in library/core/src/marker.rs, around the referenced line, and compare it with the documentation change in PR #103413. Clarify the meaning of the statement about PhantomData ownership so readers know when it applies and what to do when a type owns T; the documentation should no longer leave the reported question ambiguous.