I'm going to chime in and say that trifoliate is a subset of whorled. It just specifies how many petioles are at each of the nodes. But I'm not sure either. I just use 'whorled' and call it good. It's halfway moot anyway, since they grow out of it at sexual maturity.
On the plus side, if you pinch the plant BEFORE it matures, you get a beautiful 3-branched main stem structure on the finished plant, with a nice flatter top than just a pair of main leads.