Unified as in there is the one main ceremony that includes ALL graduating students.
The smaller ones are in addition to the main one, so those who can attend any of those also attend the main one first.
The argument Columbia had used was that there are various student associations who have been engaging in this practice, this would be akin to them but focusing on minorties.
I don't know about funding, I didn't bother attending mine (I had dropped in and out of my uni a few times, and by the time I graduated everyone I had known was gone. The ones I met upon that final return were from other years, and the school irked me, so......).
As schools fund student activities, perhaps these are paid for as part of that expense by the school.