You are not practicing sword. You practice something with bokken. I don't think you can learn how to cut correctly by practicing aikiken. Sign up to learn iaido (or some koryu ) with knowledgeable instructor, he will teach you how to cut.
Szczepan- Toby Threadgill sensei is yelling at you, by proxy, through his reply
to me. OK that was a tongue-in-cheek statement, but that thread (and the posts after that one) really address your (and my) concern.
Even if we don't become swordsmen, we can learn something valuable from swinging a stick. I don't mean "make your taijutsu better" either, I mean: swinging a stick lets you practice something really fundamental. Among whatever other things it can teach you.
It's a simple motion, if you can't form a "bridge between heaven and earth" while doing that, then it tells you something is up with your body (and/or mind), right? Hence the OP. I think suburi is a very rich practice medium. After all, aikido is about perfecting the self, not just doing taijutsu.