I'm pretty sure they mentioned that Garlemald ran into primals originally in Othard. I could be wrong though. Regardless, in most cases its the Garlean actions that have triggered most of the beast tribes to resorting to summoning primals. The Sahagin and the Sylphs certainly would probably have not considered it if it wasn't for the repercussions of Garlean actions. We have been outright told in HW that the Gnath are the first beast tribe to resort to summoning purely for the sake of conquest rather than out of fear and desperation.

I suspect we will have to deal with Garlemald proper at some point. There is no way the Ascians would be ignoring such a large player in world events. They almost certainly have their fingers in that pie. We aren't going to end conflict with Garlemald by just continually beating them up when they invade.