Any chain leveraging interoperability with ETH in order to bootstrap is arguably an L2 scaling solution for ETH. Including Solana. Assets will migrate onto L2s according to friction and trust
The big difference is that Solana and other L1s can stand on their own without needing to live on ETH; the interoperability is just a bonus perk to help get initial adoption and connect the ecosystem.
Stand it's own in what sense? There is zero economic activity on SOL.
Tapping into ETHs network effect and DeFi ecosystem is essential to gaining traction, it's not just a perk. Your building a Dex on a ghost chain and expect everyone to show up cuz it's fast.
I think that would be a death sentence if it were all we were doing.
But we're moving a TON of things around to get as much of a network as we can on Serum and Solana.