That's economics for you! Your perception doesn't not much reality. The idea that because you can redeem at face value for 1:1 and you have stronger guarantees, then it should have a less volatile price.

In reality, it comes down to market makers and market adoption/liquidity. That's why Tether could keep the beg at 1:1 despite having very little liquid cash. Liquidity will come from investors, and actually the more the better. Smaller fish like GUSD will not have that much interest from market makers.