lightning is a peer to peer payment network.
ecash is a client-server architecture.
if you actually tried running a lightning node you'd understand.
a CUSTODIAL lightning wallet is no different from a CUSTODIAL bitcoin wallet. you are trusting someone. in both cases, the custodian holds the keys.
not your keys, not your coins.
when you run a lightning node, it's two keys involved, but it doesn't change the situation because you can't cheat the other party in the pair without incurrring a bitcoin onchain transaction fee.
and the fact that this is the total risk of it, means it's just one degree less than trustless. where the custodial relationship is 100% in favor of the custodian.