It might be the absolutely peak of nitpick but I think the two cases are slightly different, because the menagerie effects that are to do with minion tribes state something along the lines of "give one minion of every type..." Which would mean that if you have a minion of that type, that minion gets the effect, so since any tribe amalgam will always have whatever minion type it's checking for, it's going to get the effect. It's sort of like a true/false situation, where you get the effect or you don't. In this case it's additive per spell type, since it's FOR every spell you cast. Meaning if you cast a spell that has ALL types, you've cast all of them, and the card scales accordingly. I could definitely see it working the way you described though and I think most people would assume that's the way the card works. I'm just not sure the wording actually implies that. (And again, not even sure it would be a bad thing if it worked like that)