I have three patterns, and two of them have three rates, while one of them has only two rates. I am not likely to use that one again though. It was my first rate when I got my pump. It's only there for nostalgia now.
I think according to Think Like a Pancreas, the issue is not how many rates you have, but how many peaks and troughs. Scheiner says "our objective is to mimic normal physiology as closely as possible. A healthy pancreas secretes basal insulin in a circadian pattern, based mainly on how other hormone levels vary through the course of a full day. It produces more basal insulin at certain hours, less at others. Normally there is one peak period and one valley period - not multiple peaks and valleys. A basal program that includes multiple peaks and valleys is almost always incorrect - or at least compensating for some other aspect of the insulin program that is not set up properly.'
Of course, aiming for one peak and one valley doesn't mean you can't have ten rates. It just means they should be gradually stepping up or stepping down, and not bouncing back and forth from high to low.