That's weird and afaik should not happen.
A quick check with fresh Xcode 13.4.1 iOS and macOS playgrounds gives the expected error message Value of type 'Car' does not conform to specified type 'Sendable'.
I don't have a newer Xcode handy atm to test, but perhaps this is a bug you should report? I'd be very surprised if there was a recent change that actually gives that class implicit conformance as I don't think that's even feasible...
It could also be that it is related to your previous post (I just noticed it's you), in that due to this being a command line project it "overlooks" this also concurrency related error, but then I'm surprised it catches on in a simple playground this time...