When requesting review on a change in those areas, if you don't mind who will do the review, you can add r?#animation or r?#svg (or #firefox-animation-reviewers or #firefox-svg-reviewers, the full group names) on the patch and it should appear on the Phabricator homepage for all of the group members.
When reviewing a change that's been directed to the group, I suggest doing it on behalf of yourself, and not the group. So when choosing Accept Changes from the drop down, you untick the #firefox-animation-reviewers or #firefox-svg-reviewers box and leave yourself ticked. That way when the change lands the commit message won't contain the group name.
We had talked about review groups for the rest of Layout, but it's still unclear how best to split that up into useful groups, so we'll leave it for now.