Oh good question.
Presumably spells they add to the summoner spell list aren't broken strong for the level they are adding it at, so I'd think both. But I'm not sure if there's anything official on this.
Summoners gain access to the following spells. Because they aren't always allowed for every type of character, spells from Pathfinder Roleplaying Game: Advanced Race Guide, Pathfinder Roleplaying Game: Monster Codex, and Pathfinder Roleplaying Game: Mythic Adventures aren't included in these lists. Such spells are cast at the levels indicated in those sources.
That's about all that is said on the matter, so it could very easily be interpreted in either direction. It may be worth a FAQ, but since it's unchained, which is just houserules anyway, I think it just needs a clarification from the PFS leadership.