Actually it's not, at least according to the "patch notes." It used to work fine. Then there was a patch about six months ago that "fixed" it. The patch notes said multiple dispatch was enabled, but in fact the patch broke it. Before the "fix" it worked fine. After the patch it didn't work, but gave an error when you tried to learn a second one. A couple patches later it became a silent failure instead of a warning. Still doesn't work as advertised (i.e., how it did before the "fix").
Actually I remember it being a 100% fail rate for a second try pre-"Fix"