It might be, though I think he was talking more about exploiting the kicks and knees to the head rule, where as I'm trying to avoid that need altogether. If an opponent throws a knee or a kick, the low center of gravity makes it easy to go for the other leg and catch an easy takedown. While this is considerably harder with knees, it's still very functional.
This entry made me think of the Ultimate Fighter episode when Rich Franklin was telling Matt Serra to go into the fight on his knees. I never really understood what he was going for, but after reading this post I can't help but wonder if that's what he meant.
I like the creativity of this setup: presenting the backdoor sweep, available for a shot, can't be kicked in the head (in MMA at least), it's a good perspective. The only thing I wonder about is: if the opponent is significantly taller, aren't you giving him a stronger base by allowing him to push with his legs whereas you can't ... while on your knees? It almost sounds like a move that you have to be prepared to immediately react to your opponent instead of offensively take action (i.e. - if he steps back shoot asap so you don't eat a punch, if he leans in sweep asap so he doesn't gain too much control for a takedown/pass).
This is definitely a heavily reactive position, and it requires some reflexes and alot of practice.
As for dealing with a taller opponent, you are going to be coming up under him even more, so it actually gives you considerably more leverage, allowing you to get your legs under you even more and go right through his torso.
Personally, I've never had a problem with height fighting this way, and my opponents and training partners are generally taller than me (as is the Judoka I was originally trying this on). The point is to take his legs away, either with the leg-grabbing takedown or the sweep, so I don't think it should present any more of a problem than you would have standing up.