let me put it in simple terms w/o numbers.
you're taking a chunk of coin off a very secure ledger and moving them over to a less secure ledger. it's too be expected those coins moved will be worth less b/c they are now less secure.
b/c of arbitrage, you can expect the moved coin to drag down the price of the not moved coin to a lower equilibrium.
But why will you move the coins in the first place???
for experimentation, speculation, stupidity, pump and dump, who knows? we know it will occur.
But why will you sell them for a lower price instead of transfering them back to BTC?
you don't have to do anything. the arb bots will take care of it for you.
What??? Someone have to sell the cheap coins?
do you seriously think that when a SC is first established on Day 1, 1 scBTC = 1 BTC in fiat terms?. it can't be b/c of newness, less security, chance of failure, etc. with time, as it proves itself, the arb bots will equilibrate the price but at a lower level b/c of the always present risk of failure of the SC. the SC is
not Bitcoin.