The goal of TBTC is not a price peg to BTC, it is designed for redeem-ability.
1 TBTC is always backed by 1 BTC
It is expected that liquidity incentives could cause TBTC to have a higher price than BTC
It’s worth noting that the ETH bond and KEEP stakes are used as an additional layer of security to ensure the security of your BTC. The network is quite efficient at liquidating operators that let their Keeps become under collateralised due to the reporter incentive.