Update release notes around dynamic type checks

source/release/note/2.5.12.rst

@@ -12,7 +12,7 @@ Stratego
 
 Stratego has two new reserved words: ``cast`` and ``is``. Local variables can be reserved words if they start with ``'``, so you can use ``'cast`` and ``'is``.
 
-Under the Stratego language options in your ``metaborg.yaml`` file you can turn on the gradual type system, if you use the incremental compiler. This option is ``gradual: static``, and only tests the types statically. The default is ``gradual: none`` right now, meaning the gradual type system is not on by default. There is an experimental third option ``gradual: dynamic`` which not only checks the types statically but also inserts casts to check types dynamically where necessary.
+Under the Stratego language options in your ``metaborg.yaml`` file you can turn on the gradual type system, if you use the incremental compiler. This option is ``gradual: static``, and only tests the types statically. The default is ``gradual: none`` right now, meaning the gradual type system is not on by default. The ``is`` dynamic type check is not yet supported at runtime, you may get Java compilation errors when attempting to compile Stratego code with that. Dynamic type casts inserted by the gradual type system are also forthcoming, runtime support for this is not yet ready. 
 
 NaBL2
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