Clarify which portions of requires-python behavior are consistent with pip

docs/pip/compatibility.md

@@ -447,14 +447,16 @@ By default, uv does not write any index URLs to the output file, while `pip-comp
 in the output file, pass the `--emit-index-url` flag to `uv pip compile`. Unlike `pip-compile`, uv
 will include all index URLs when `--emit-index-url` is passed, including the default index URL.
 
-## `requires-python` enforcement
+## `requires-python` upper bounds
 
 When evaluating `requires-python` ranges for dependencies, uv only considers lower bounds and
 ignores upper bounds entirely. For example, `>=3.8, <4` is treated as `>=3.8`. Respecting upper
 bounds on `requires-python` often leads to formally correct but practically incorrect resolutions,
 as, e.g., resolvers will backtrack to the first published version that omits the upper bound (see:
 [`Requires-Python` upper limits](https://discuss.python.org/t/requires-python-upper-limits/12663)).
 
+## `requires-python` specifiers
+
 When evaluating Python versions against `requires-python` specifiers, uv truncates the candidate
 version to the major, minor, and patch components, ignoring (e.g.) pre-release and post-release
 identifiers.