fix: use __dict__ lookup in _get_class_flags to fix diamond inheritan…

skbase/base/_tagmanager.py

@@ -35,11 +35,13 @@ class attribute via nested inheritance. NOT overridden by dynamic
         # We exclude the last two parent classes: sklearn.base.BaseEstimator and
         # the basic Python object.
         for parent_class in reversed(inspect.getmro(cls)[:-2]):
-            if hasattr(parent_class, flag_attr_name):
-                # Need the if here because mixins might not have _more_flags
-                # but might do redundant work in estimators
-                # (i.e. calling more flags on BaseEstimator multiple times)
-                more_flags = getattr(parent_class, flag_attr_name)
+            if flag_attr_name in parent_class.__dict__:
+                # Use __dict__ lookup instead of hasattr/getattr to avoid
+                # MRO traversal. getattr would cause classes that don't define
+                # the flag attribute in their own class body to act as proxies
+                # for their ancestors, re-injecting already-superseded values
+                # in diamond inheritance scenarios.
+                more_flags = parent_class.__dict__[flag_attr_name]
                 collected_flags.update(more_flags)
 
         return deepcopy(collected_flags)