“This unusual pattern indicates that the weakness is intentionally hidden to limit the security level to 40 bit by design.”
GEA-1 claimed 64-bit security and delivered 40, through a key setup the authors say is highly unlikely to happen by chance. The attack needs just 65 bits of known keystream and 44.5 GiB of memory. Somebody chose that weakness on purpose and shipped it in a mobile data standard. Every “lawful access” backdoor eventually becomes everyone’s access.