But I'm not sure that these arguments are strong enough to show that SPV sidechains hurt Bitcoin's sound-money property. In my opinion, this is only possible in Case #3, but, like Erdogan implied, it might be highly unlikely (impossible?) for a sidechain to obtain the status of #3.
The problem for scBTC in case #3, is that it first will have to survive a period with less freefloating value, so it will have a problem achiveing the status of #3.
Others would claim that a #3 is ultimately inevitable due to the ossification of Bitcoin.
At some point there would become a new SC that would be better in every way for everyone than Bitcoin and those that can exit do when then can do so.