There's some confusion here. Vodafone aren't talking about Openreachs line cards.
Mark has gone on to discuss Openreach FTTC DSLAM line cards in that article which certainly confuses matters but I don't believe Vodafone were blaming the DSLAM line cards.
"We are in the process of upgrading our network configuration and discovered a technical issue with some line cards which means a small number of customers may experience slower speeds when accessing certain sites. This has nothing to do with throttling or traffic management, which we do not use on our broadband service. We are working hard to fix the issue in order to give any customer affected a great online experience. We’re sorry for any inconvenience caused."
I'd love to know how they managed to test Openreach's line cards and how they intend to deploy a fix.
I would safely assume they didn't mean the DSLAM line cards at all, but rather their own equipment.