Actually, teleporting an *overloaded* ox or henchman is definitely an exploit comparable to crabwalking, now that I think about it. Why? Because encumbrance is a deliberately imposed penalty that the player is circumventing through programming limitations. Escaping it is not a lucky convenience.
In thinking about this discussion as something that could be applied more universally to look at whether a behavior is simply corner-cutting for convenience or a punishment-worthy exploit, these are some criteria I'd use:
1) Does it allow the player to avoid *intentional* inconveniences (and perhaps encounters) that developers have invested time in programming? On this scale, I think teleporting an ox is not significantly different than walking around known triggers, for example. But avoiding encumbrance through crab-walking or teleporting an *overloaded* henchman/ox is egregious because encumbrance is a significant feature of the game. A "yes" to this question means the behavior is almost certainly an exploit.
2) Does the behavior affect game balance vis a vis other players? One way to answer this is "how much is it available to every character on the server"? If every character can do it, then it's unlikely to affect this part of game balance.
3) Does the behavior affect game balance versus the game itself? That is, if some players engage in it, do other players then have to do the same to "keep up"? As a comparison, allowing steroids in a sport makes them available for everyone, but it also means you probably can't compete unless you're on steroids. (I don't find the teleporting ox means other players have to teleport theirs or be put at a big disadvantage.)
4) Does the behavior affect the enjoyment of other players? Further, can the player engaging in it mitigate this effect? In other words, if my character does not see it happening, does it still have an impact on me in some way? This is more a "bad form" question and hopefully could be worked out in game. As an example, "tells" are an (intentional) bypassing of the in-game, IC mechanical limitations. I really don't like them, but they're a necessary evil. Even though tells are allowed, there are many cases in which a "tell" is "bad form." (In contrast to a critical tell, that some character somewhere is teleporting an ox around can be quite anodyne.)
5) Can the behavior be role-played as reasonable?