@Pablo yup the 3.10 opcache used tp_version_tag. But it also does identity (pointer) comparison of type/class object https://github.com/python/cpython/blob/3.10/Python/ceval.c#L3432. Which is why it doesn't fail.

I created this issue because we don't do type pointer comparisons anymore in 3.11's new specialization infrastructure, and rely only on tp_version_tag and dict keys version.