Revert "DataForm: Streamline validation behavior"

[oandregal]

What

Reverts #71345

Why

See #71345 (comment)

[github-actions]

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[oandregal]

The CHANGELOG check is failing because this actually removes an entry from the Changelog without adding one. This is expected and fine. I'll land the PR ignoring that check.

[github-actions]

Flaky tests detected in d8eb424.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/17244004739
📝 Reported issues:

• [Flaky Test] should refresh the page when stylesheet loading fails #71135 in /test/e2e/specs/interactivity/router-styles.spec.ts

[oandregal]

I'm going to revert this one to make sure it doesn't make it to any npm release / gutenberg RC, and so that we can take the time necessary to fix the issues reported.