YEs the spikes are for dialing in the height. In my room setup I preferred the taller spikes on the X5s and my ears at the bottom or just below the tweeters. I know many prefer the sound with their ears at the middle of the tweeters which is what I did for some time but when I raised the height of the speakers and changed my listening chair vocals and instruments really locked into place and the focus was better in my opinion.
Most likely the distance between the speakers, distance to listening position, toe in, distance to side and back walls would influence this.