But think about a few things. There's a general sense of what an undergraduate education looks like, 4 years, prerequisites followed by picking a major, etc.
"Grad school," on the other hand, is kind of meaningless. Is it a master's program? PhD? Is it in a hard science? English? It it in a trade a la journalism?
So my assumption is that every program is different and every school does it differently for grad programs. They're small and weird enough that they have to.
I do think there's a lot more faculty involvement in grad school admissions. I also think that master's programs are much, much easier to get into than people suspect. I went to the one of the top journalism schools in the country, and as far as I could tell, it had about a 50% admission rate. 50%!!!!!