Are we not _already_ attempting security by obscurity at the very moment we talk about "exposing your LAN" as a supposed weakness of IPv6? /64 is the smallest

Are we not _already_ attempting security by obscurity at the very moment we talk about "exposing your LAN" as a supposed weakness of IPv6? /64 is the smallest network your ISP can hand out, of course you can rely on that. Even my mobile phone is getting a /64 from my ISP.