iPhone trade-in £50 promotion terms - ‘working phone’?

I recently sent a phone for trade-in which has a cracked screen and is eligible for £15 as confirmed via email. The phone works fine but the email suggests it is a ‘non working phone’ whatever that means.

I’m happy to accept the £15 provided I get the £50 trade-in credit bonus that was offered as part of my new plan. The t&cs however as vague as to whether the phone is eligible. 
 

ID state the following: 

“If you’re looking to take advantage of a trade-in promotion when buying a new mobile, please keep in mind that recyclable phones or devices with ZERO value (Beyond Economical Repair) do not qualify towards any promotion and no additional value will be paid.”

However on this page they are at pains to say it apples yo ‘working’ phones for which it would seem my phone does not reach their definition.

which one is it? It would be helpful to know before deciding whether to get the phone back and sell it instead

Thanks!