The confirmation is just if you're setting up any kind of auto-forwarding. If you are manually forwarding, there is an obvious human involvement, but once you set up some auto-forwarding, the human is removed. If you have a group that you want to forward to normally, and regularly, it makes sense to set up a Google Group like this one which people can join/leave. If you've set it up, then you own it and can easily do the confirmation for your GMail account to forward it to the Google Group, which will in turn deliver it to the people who want to receive it.
I suspect Google switched to the confirmation of automated forwards so that spammers couldn't use a free GMail account as a way of reaching people, and hiding who they were.