Do only some Ionia paths get a huge bonus if you hit 10 Ionia, and if so why isn't this better indicated in game?

About a week ago I had an Ionia game where I found an Emblem. I excitedly spent as much gold as fast as possible to get 10 Ionia in, upon which I slammed the emblem and watched as it proceeded to do... Nothing?

The trait said 10 Ionia, but it was Gold not Prismatic and watching videos online it really didn't appear as though it had any of the intended effects. I still went 2nd so I brushed it off and moved on.

Come to find out today, in another game today, where I was going Ionia again, this time Yasuo/Yone that - in fact - in this game Prismatic Ionia was a thing, because one guy went for it while I was re-rolling for Yasuo/Yone and knocked me right out of top 4.

In the trait description there wasn't any indication that 10 Ionia was a thing. I'm not sure if how this mechanic works has changed over the course of several patches (started playing this set at 16.4). Seriously, am I missing something? I'm so confused.