Honing, in theory I think, is pretty simple. And when your thinking about setting a bevel and even just basic sharpening you can go straight down the hone. When your really trying to apply the fin to the edge you want the striations aligned evenly (and with an opposing angle on each side of course) for each stroke and if you run down the hone angling the razor it gets wavy because your wrist would need to compensate. With an x pattern your just pulling more and twisting less. Although it sounds hard, in practice its pretty easy.

An x pattern also compensates for the dishing that can occur in the center of the stone a little better too.

You'll see the big wide stones in factories being used to set the bevel and (for the most part) sharpen a razor. Many personal users didn't typically have 3 inch stones.

I think that pressure distribution theory may have some merit as well.

I use an x pattern a lot in honing but not always in the beginning of the process.