I think this is generally a good idea, but only in the right circumstances. The PR adds the text to the general “removal process” section, which might also be used when a still maintained collection is removed for other reasons.
I would probably adjust the text to make clear that these steps should only be followed in case the collection is removed because it is unmaintained.
(If you’re wondering about other scenarios: since we’re discussing potentially reducing the Ansible package size, we might also want to remove collections for other reasons - like thinking they are not useful for the majority of users - in the future.)