Isolated FIN Margin is a type of margin product that allows leverage trading of up to 2.5X on certain FIN trading pairs. Margin is allowed on most USK collateral types when paired with USK on FIN. Currently margin is only unavailable for gPAXG (Paxos Gold bridged over to Kujira using Gravity Bridge). All margin liquidations are handled by ORCA. Read more specifics about how Isolated FIN margin works here.
At the moment, based on the underlying mechanism for isolated FIN margin, ORCA liquidations for FIN margin are handled in the same queues and markets where USK collateral is liquidated and bidded on using USK. This is why FIN margin's relationship with ORCA can be understood as it simply being a subset of ORCA USK markets. This is because using FIN margin effectively just means minting USK in reverse and backing it immediately after. Read here for a complete explanation of this process. Due to the above, the isolated FIN margin ORCA markets literally double as the USK liquidation markets used for liquidating USK collateral. Read here for more about how USK works and here for its connection to ORCA.