The seemingly random 100 point items, if I'm not mistaken (other than the repeat event items like Rounsey Wand) are all things needed for various Mog Garden quests, which is probably meant to help people along with clearing their quests in order to get to the two new ones they added this patch for the other two mounts.
EDIT: Not necessarily quests, but now that I take another look at it, some of those are items needed to evolve certain monsters in Monster Rearing. I specifically remember going on an... adventure to Purgonorgo Isle to obtain Bibiki Slugs through clamming (I have all of the Monster Rearing mementos). That was like a blast to 10 years or so in the past. As far as I know there isn't any other way to acquire the slugs.
Edited, Jul 9th 2016 12:43am by Fynlar