I don't know that it was that many, but it's worth being clear that it was always 2 worlds that were 1/2 or less full merged into one. Also worth noting that it was voluntary, so everyone who was initially merged went into it being okay with it - it wasn't forced.
As for WIS feedback, I don't know that they ever spoke out on it. I do remember that they were set to merge 2 worlds a while back, but the one never signed off because they didn't want to lose their history, so eventually both filled and kept going seperately.