Yea it's really weird that it works with RNG, I honestly thought it was a bug as well.
The Knucklebone Tokens were added because failing to get a wild wolf too many times in a row is just really disheartening. But now, even if you have all of the tokens because of your bad luck, you still have to rely on RNG to get the wolf hunt to appear. Which kind of defeats the point doesn't it? Not to mention, unlike finding wild wolf encounters, you are limited to 5 tries in one day. Maybe a little more because of the auto rerolls, or completing hunts. But still, if you want to try and get a WW hunt, you probably won't be doing a lot of other hunts anyway. And even if you did, some of them take hours to complete. Which means that you are now not only limited by RNG, but also by time.
If the worry is that Wild Wolves will become too common without this RNG, I would honestly prefer it if the amount of tokens is raised back to 100 instead. At least than you really are guaranteed to get the wolf you were promised, even if it takes longer to get there. Though I'm sure that is a very unpopular opinion.
I think giving it a separate hunt slot makes the most sense, but I don't mind it being a part of the regular hunt slots. This would automatically put a limit on the amount of WWs you could find at once, which is good in my opinion. I definitely do feel it should be possible to have more than one going at once though. Which, I'm guessing now, is probably already possible, just no one has been lucky enough to try it.