Answer
No — that auto-generated CFP package is fully regenerated and overwritten whenever any attribute on the corresponding custom LU is added, changed, or republished, which silently discards any manual edits made directly to it. The durable way to add extra validation logic when a custom field value is saved is to implement it via a Custom Event triggered on the underlying custom field table (the CFT) for new or modified records — once the specific field is created or modified, run your validation logic there, and trigger error messages, Streams notifications, or emails as needed, rather than hand-editing the auto-generated CFP package directly.