Call to Arms support. GGG please clarify before ruining many leaguestarts

There is way too much confusion around this support gem and what it actually does. In the video, it clearly applies multiple warcries but in the interview with zizaran on 3/26, Mark states that multiple warcries are not triggered by call to arms.

please please please just clarify what the actual function of this gem is. A lot of people (myself included) have shown a lot of interest and hope for a warcry based slam build this league as a possibility, but risking a league start on conflicting sources of information feels awful.

I don't need a discussion on why this decision was made or why CTA was moved to a gem slot instead of the passive tree, just please definitively clarify with 100% certainty what exactly this support gem does.