Here is where you are flatly wrong. There clearly is an incentive, the time incentive.
To change BTC to scBTC, you will have to wait for 100 blocks or so, whatever the confirmation time may be.
If you buy them at exchange, there is no wait.
This confirmation exchange value is created in both ways in the transaction. People will pay a premium for time, localbitcoin pricing is evidence enough of this.
But you are assuming that there is an incremental demand for the scBTC, whatever its utility is. This is not necessarily the case.
You need someone to buy all those scBTC you want to dump for fiat.
Since BTC & scBTC price are correlated one does not need to buy scBTC to "ride your pump"
So is there a peg or not?
Is it just "correlated" now?
Let's assume the SC has some feature or other, faster, more private, whatever it is doesn't matter, we can pick whichever one is most successful and has the most liquidity at the moment to take advantage of the time premium and do this.