the article has an update that says it was reverted

Update: Apple has reverted the page to its previous behavior. However, sources within Apple corporate not authorized to speak on behalf of the company acknowledged that requiring a validated user was intentional, and may return.

Hmmm.... I can still use
https://checkcoverage.apple.com/au/en/
and check my Macbook's warranty coverage. It works just fine.
The above URL is for Australia.

I now tried
https://checkcoverage.apple.com/us/en/
and that is responding as well. But I don't have an hardware that are purchased in US, so I didn't test that out.