is core still just a subset of std?

In this thread from 6 years ago (https://old.reddit.com/r/rust/comments/bpmy21/what_is_the_rust_core_crate/), some people suggest core is just a subset of std.

But I did a diff of the list of modules listed on https://doc.rust-lang.org/stable/core/index.html vs. https://doc.rust-lang.org/stable/std/index.html and it looks like there are some modules (e.g. contracts, unicode, ub_checks) in core that aren't in std.

Diff results: https://www.diffchecker.com/AtLDoH4U/

This makes me wonder: is it even safe to assume that if an identically NAMED module exist both in core and std, that the CONTENT of both modules are identical? The only reason I think this may matter is that when I "go to definition" in my IDE I often end up in some Rust source file in the core crate, and I wonder whether I can safely assume that whatever I read there can be relied upon to be no different than what I'd find in the std crate.