I've been there. Management was fine with the testing but it added too much overhead for nearly no benefit to us.

One more thing to troubleshoot at 3 am, one more thing to teach to a disinterested tier 1 support team, one more thing for Chrome to be weird about, hundreds more rules to manage in a hostile load balancer, logging tools that don't understand ipv6.

Turned it off. End customer asked why the site got a little slower (CGN) and when we can turn ipv6 back on. As far as I know it's still on the backlog.