There are definately some interesting economics going on here, it doesn't work how you might expect.
Stronger SBD pegging could even improve the price of Steem, as more people from the great crypto economy use it as a hedge against falling crypto prices. More eyes and utility from this network = higher price for its token .

Also since SBD is technically only an IOU for $1 of STEEM, stronger SBD = more faith in the ability to extract $1 USD ea from the network in the future.

This is my first tweak of the APR parameter since becoming a witness, I'll be monitoring both price and other witnesses votes closely to see if this was the right choice or not because you're right, the balance is crucial here