You were right up to this point. Medical devices requiring a prescription must be obtained via specialized suppliers, like a pharmacy for hardware. These appliances are not sold directly to end users because they can be dangerous if misused. This includes even CPAP machines.

In theory, that written offer only needs to go to the device suppliers. Who almost universally have no interest in source code. When the device is transferred or resold to you, it need not be accompanied by the offer of source.

If that was true, anyone reselling an Android phone could open themselves up to legal liability. Imagine your average eBayer forgetting to include an Open Source Software Notice along with some fingerprint-encrusted phone.