Readme: clarify behaviour of composer (#60)

README.md

@@ -57,6 +57,9 @@ Typically, you have PSR-4 autoloading which often solves this problem for you, b
 And in such cases, the test may work when executed in standalone run, but fail when running all the tests together (depending on which class was autoloaded first).
 Therefore, having a collision detector in CI might be useful.
 
+## Composer's Ambiguous class resolution
+You may have thought that Composer itself is somehow solving this, but that is not true. The only similar check that Composer performs (which results in `Warning: Ambiguous class resolution`) happens when classes collide **inside** the `vendor` path, not in your codebase. Composer does not report class ambiguity in your project at all.
+
 ## Supported PHP versions
 - PHP 7.2 - PHP 8.3