Skills that are largely missing from full rack banks are thin cuts, carom shots played intentionally, break shots, combination shots, and multi-rail cue ball position play. There are quite a few shots played with minimal attention played to position. While the two way shot aspect of bank pool is of comparable complexity to that of one pocket, the defensive play in bank pool requires a bit less speed control than what is required in one pocket, straight pool, and rotation games.
Bank pool players need to have great skills and they always put on a great show, but I think that straight pool and one pocket are better tests of pure skills over the green felt.
Finally, I do not agree that the break doesn't matter in bank pool. Having the first shot is a big deal at the highest level, and there is ample motivation to fix the rack for those inclined to do so. At high level, the game in which the break shot matters the least is definitely straight pool.
Full rack banks is a beautiful game and a serious test of pool, but I'd have to disagree that it's a more pure test of skill than the other games.