My old WFCO had a pass through.
I think that means when there is shore power the shore power could pass through to the dedicated inverter receptacles.
If you already installed a new inverter and it works I would remove the old WFCO and terminate both lines.
I would label the terminated lines for the next guy.
Randy and Beth 15 F250, 16 30' International, ProPride, Dexter 3" lift, Michelin 16, Dill TPMS, Centramatics, Battleborn x4, Victron BMV and 1.2KW inverter, Orion DC/DC, BlueSolar MPPT, 300W solar, Alpine iLX, Polk MM1, Samsung smart 42"