I don't think the question turns on unreasonable searches. Apple isn't being searched here. Instead, the question is whether the All Writs Act grants sufficie

I don't think the question turns on unreasonable searches. Apple isn't being searched here. Instead, the question is whether the All Writs Act grants sufficient power to compel a company, third-party to the action, to build a tool for breaking into its product. This is different to your telephone interception example, because that interception is authorised by a specific statute, not using a general writ issued under the All Writs Act. The argument here is executive overreach - that they should be asking the legislature to pass a law specifically to require this kind of assistance, rather than using the All Writs Act.