The first thing that importlib.reload() does is to verify that the passed module is an instance of types.ModuleType (Lib/importlib/__init__.py:107).  This check seems unnecessary to me.  We really don't have a functional need for the check (that I know of).  Furthermore, there has been at least one serious proposal recently that suggested using custom module types.

The only benefit that I can think of to the type check is it makes the failure more clear when someone tries to "reload" an attribute in a module (thinking just the attribute will get reloaded!).  However, does that matter all that much now that reload() is not a builtin (ergo less likely to get misused very often)?

I'm not invested in removing these 2 lines (or at least loosening the restriction).  I've brought it up simply because it keeps staring me in the face lately. :-)  If anyone has any objections, I'll drop it (at least it will be recorded here in the tracker).  That said, I'm glad to remove the restriction otherwise.