Sorry I thought people were saying that Cineworld is telling them to pick up their tickets 20min prior or they will be cancelled. When in fact the website says they will be cancelled 10min after the show start time (which they aren't enforcing as you say).
That's what the Unlimited Online Booking Terms and Conditions says
Originally Posted by Terms and Conditions for the Unlimited card online ticket booking offer
18.10 Any ticket booked online using an Unlimited Card must be collected no later than 20 minutes before the advertised screening time on the day of performance otherwise Cineworld may release it for general sale. No refunds will be given.