“But web standards can be incomplete and have flaws.”

Yes.

“In that case, the standard needs to be changed”

No. At least not in a breaking way. Browsers are full of implementations of web standards that in hindsight were flawed, yet still continue the support that flawed implementation. It’s part of the promise of the web: backwards compatibility.

Fair point btw on this not yet being a W3C recommendation yet. It may be perceived and used as a standard given the large amount of implementations by browsers, but technically indeed it’s not a standard.