The amount of USDC locked in the Layer 1 bridge contract remains unchanged through the entire process, meaning deUSDC on both Arbitrum and Optimism remains 100% collateralised and fully redeemable for the Ethereum-locked USDC.
When slippage in the AMM pool occurs (when deUSDC or USDC is removed or inserted from the pool), external LPs are incentivised to rebalance the pools by either depositing more funds or withdrawing funds back to Ethereum via the official Arbitrum and Optimism bridges (the simple lock and mint bridges), with a wait/challenge time, before redeeming for the underlying locked assets.
The Hop bridge works in much the same way, and both Hop & DeBridge operate slashing to encourage validator nodes to remain honest and to keep the bridges functioning within service level agreements, or SLAs.
Advantages
The use of specialised bridging assets in an AMM pool, as an intermediary step in the bridging process, effectively incentivises liquidity where it is needed in the system while allowing external liquidity providers to capture arbitrage profits resulting from slippage.
Disadvantages
This approach can be more costly to users, as instead of offering a 1:1 exchange rate across the bridge, the AMM pools result in slippage.
There are also risks to LPs whose funds are deposited to the specialised bridge asset liquidity pools or who are holding the specialised bridge assets as a form of IOU awaiting redemption.