After finding that one of my characters received a boon from Hylea due to pledging to her in pillars one, yet another didn't for her pledge to Galawain, I tested whether Obsidian's pre-created Galawain history would receive a boon. Since I didn't receive on there either, I decided to waste some time testing every pledge to see which ones received a boon and which didn't.
I used the pre-created POE1-histories for each god except Skaen, since it wasn't entirely clear whether that one involves actually pledging to him: for that one, I only filled in the Hollowborn Crisis choices, including pledging to Skaen alone, and sending the souls to Woedica.
Results: only the Characters who pledged to Berath and Hylea received a reward, "Berath's Black Bell" and "Hylea's Bounty" respectively, available in the armoire in the cabin you revive in. The others choices either aren't supposed to grant a reward, or are bugged. Unfortunately, i couldn't attach the .savegame files here, and find myself unable to insert screenshots of the ones with boons without screwing this post up.