Doubtful, sigv2 is not supported in all regions. So all current software that wants to be compatible with more than a portion of regions has to be compatible.

Doubtful, sigv2 is not supported in all regions. So all current software that wants to be compatible with more than a portion of regions has to be compatible. This is a great way of introducing breaking changes. Imagine that for example, ipv6 would be at near 100% adoption if "new websites" were only available over v6.