"I am the owner of a number of Google Groups. In one of them (ufpcboard), when I click on "invite members", I am taken directly to a screen to "invite people by email", rather than being also given the option "Add members directly".
Why would I not have this option on this one Group?"
Ans:
"Thanks for posting your question here on the forum. We have removed the "Add members directly" option for all Adult groups, so I'm assuming that's why you aren't seeing the option in yours. This is a policy decision that we made to protect our users. If you feel your group has been mistakenly categorized as Adult, you can remove it by by accessing Group settings -> Categories.