Sure, maybe anyways but let's assume it is, the parties to that contract are the manufacturer and the copyright holder. The contract allows the manufacturer to distribute it to the distributor without requiring the distributor to agree to the terms and itself become a party. The distributor can then sell the device with the software on it on without acquiring a license and becoming a party to the contract because the copyright has been exhausted (first sale doctrine).

EULA's get around this by forcing the end user to become a party to the contract via a click wrap agreement. There is usually no such click wrap agreement binding the distributor in the case of the GPL. And the GPL doesn't require the creation or maintenance of such a click wrap agreement so the manufacturer would be free to remove it even if the original software had one.