The bridge is trusted. Users of the same Ark can pay each other similarly to Lightning, but to get into the Ark in the first place (either via Lightning or yet another Ark that has to use Lightning) the ASP is the spender on the inbound swap and can collude with itself. A chain payment to the Ark may be trustless if you can afford it, but again that's pointless as you can just open a channel, which is why they have to scam and call it Lightning for poors.