Indeed we have already this statement.
But I think supporting one LTS is a little bit too strict as it is possible for user to stay supported with LTS by skipping one.
So I would be in favor of updating the release process to extend to 2 LTS. Also this rule should be put more visible on the migration category.
Also I do not think we should be strict on when we remove the code, it can stay longer if we do not find time to remove it. The rule is about what is supported, we can by chance support more.