The number of implementations was not considered a criterion for Chrome, or at least they didn't mention it. For WebP, they didn't seem to care much about it. I

The number of implementations was not considered a criterion for Chrome, or at least they didn't mention it. For WebP, they didn't seem to care much about it. I agree that it's a good criterion, as it is a good way to ensure that a spec is solid and interoperability actually works. So I am happy that there are currently three alternative jxl implementations. The main thing you want to have though, is a standard that cannot be unilaterally changed in arbitrary ways by a single party. However flawed it may be, ISO does have a long history of standardization, and it has procedures in place to ensure that changes are scrutinized and can only be applied when approved by the national standardization bodies.