You're still allowed to use the old ones that haven't been converted yet (there's just normally not much to do there on Meta). The old ones run on different rules. Anyone can see them, but you can't officially "review" them unless you have the Strunk & White badge. The new ones just won't let you in without that amount of reputation.
It wouldn't be fair to hide the link for users who can still participate in the other tasks while they're being converted to the new system, and I'm not sure what kind of reputation requirement will even be placed on those. The reputation requirement on the current ones is to match the feature you're using in that task.