Nice, the issue tracker is open 
I don’t think that there is much profit from that, but large liquidity provider will be able to say more about this. The main reason to handle it this way is to reduce API calls from the client side, i.e. the server allows for a 0.25% deviation from the actual spread, which is the exchange fee (usually around 0.2 - 0.25%, so its about 0.5% in total).
I would like to have this as separate pool. Right now all pool operations are mostly funded by shareholders. Many of them will be more than happy with the NSR reward in order to improve their voting power and influence. People who prefer a stable value payout can stay on the NBT pool.
Let’s consider the alternative: Can we really expect someone to burn 10,000 NBT at market price? I think we probably would need to pay more here.