It's also testable. Get some straw mats and a live blade, and see what happens. I think doing this would be an excellent exercise for many of the people (from many disciplines) who like to opine about swords on the web.
There are many potentially useful ways to swing one's arms while holding a piece of wood. Only some of those will make for effective cuts.
Yup. And saying that I realize I'm overdue to invite a bunch of fellow instructors and students over to my place for a BBQ and cutting session. I've got about 50 mats in the garage at the moment. Makes for a lovely afternoon. Safety discussion first, going through a few things about *not* keeping that forward leg out there, etc., actual cutting, and *then* and only then beer and BBQ... Good reality check. And it usually only adjusts one's form a bit if they're well trained. But you quickly find out what works and what doesn't work nearly as well.
All that said I fully understand that there are many reasons why one would swing or train with a bokken (or jo or whatever) in order to improve one's empty hand art. But as you said, actually cutting with a sword can be done in many ways, some better than others, some different than others (meaning styles differ and not all styles involve a casting movement, for instance), and some that don't work at all. Physics is physics and, yes, it is reproducible and repeatable.
Bokken usage to teach something in terms of *aiki* (or whatever) is a valuable teaching tool, but one should be very careful not to conflate that with good *cutting* in the *different* sense of the requirements for proper usage of an actual steel weapon when those approaches diverge. That is all. Unfortunately too many tend to interpret that sort of discussion as a critique or dismissal of the "quality" or value of bokken work in Aikido. I don't see that at all and train in it and teach it myself as well. It's just putting things in the correct context.