I asked Adam about the logic for it last year, he told me the fees go to pay for rotating the federation’s onchain utxos, to refresh the timelocks

if they dont get regularly rotated, eventually the onchain funds can be spent by a smaller emergency keys multisig

it’s a normal cost for any multisig thats using contracts with timelocked emergency spend path. basically every corporate structured multisig works this way, see anchorwatch contracts