Thanks, Raymond, for the review on GH-15216!

Shortly after posting this issue, I noticed a very similar story in CHECK_BINOP.  I've just posted GH-15448 to similarly make returns explicit there.  It basically consists of a number of repetitions of

-    CHECK_BINOP(self, other);
+    if (!PyLong_Check(self) || !PyLong_Check(other)) {
+        Py_RETURN_NOTIMPLEMENTED;
+    }

with the names `self` and `other` varying from site to site.  Though the expanded version isn't literally a `return` statement, I think it functions almost as well as one for the purposes that explicitness serves here, and much better so than a reference to `CHECK_BINOP`.