To be clear. I actually don't care at all about the change to command, personally. I was unaware the spell was ever used.
For your specific example, I feel it's out of the scope of what I'm discussing. But in my opinion, people are weird. It is not "bad DMing" to not allow abusive uses that are obviously against the intent, and rules, of the spell. In the specific case, I would simply have the "walking" end at the edge of the boat. I would have the enemy end their turn there. In the case of swim, it really doesnt matter if you follow the command. Unless danger was present in the water, its fine. It's not a big deal.
I think there is a lot of hyperbole in this discussion, and much of it is unproductive. But that is, largely, the norm around here and it does make discussions more interesting. So I am happy people feel free to engage in such wild discussions.
Except the examples I gave aren't hyperbole.

So I think sometimes it's useful to take vague statements and get to actual examples.