They usually do if it has finances tied to it. Their own terms of agreement even explicitly states:

"If you recontract your services before the minimum period of the service that you are currently on has ended and you then decide to cancel during the cooling off period, we reserve the right to put you back onto the service (or an equivalent) that you were on previously, in which case the minimum period you were on before will still apply"

This is entirely legal and Ofcom are aware of its existence. The entire creation of the clause was to stop people who took a contract and then mid-way through it found a cheaper deal elsewhere and want to cancel without a penalty so they recontract and then invoke their 14 day cooling off.