There's a couple guys that like to work this at my school, and it's either so that they won't panic when someone gets the back and they work escapes, or so they can look at other options like attacks.
There's always something to be said about giving up some of the "taboos" of BJJ, if only to learn to defend from a position you don't often find yourself in (at least not for long...), and there's always even more to learning something you may never have utilized.
Not saying you're going to develop a mean "rear mounted with the hooks in" game and discard your guard altogether or anything, but maybe you'll be able to develop a good defensive/offensive turtle if you find you're geared toward it. I often look for half guard from the bottom, rather than guard, because I really am buying into the idea that there's a lot more to be done from there... Get good, and you're halfway to the back or a sub, rather than halfway to being passed.
That said, your instructor might be getitng fired up because he doesn't want you looking at branching out and all that until you've nailed the basics. I know you only started this year, so maybe he wants you to wait on experimenting until you're a little further along.
Then you can pull that awesome "wooden tooth face crank" you've kept in the back of your head.