True pyramidal programs do not exist in civilian hospitals. Previously a program took a large group of undifferentiaed interns but did not guarantee that any of them would finish. People were fired, dropped out, etc.
Now we have a caste system where everyone who matches as a CATEGORICAL resident is essentially guaranteed a chief spot unless you are fired for cause. It's somewhat more complicated than that, but the point is that programs do not take more categorical interns than they have chief spots.
Almost all programs have more interns (and sometimes 2's and 3's) than chiefs. These people come in as prelims, however. They might hope to slip into a spot, but it's dependent on a spot opening up, no matter how good a job the person does. (FREIDA will give the appearance of a pyramidal program in this case. Even if a program 10 interns, 8 two's, 5 threes, 4 fours and 4 chiefs, it's not classically pyramidal. 4 categorical interns start, 4 finish. The rest are prelims.)
I've heard of some programs that run stealth pyramidal programs where they will fire categorical residents if they see better options in their prelims. Hard to say which are which.