"You decide doctor". What do patient preference arms in clinical trials really mean?

It is well established that random assignment between experimental treatment and control arms is the gold standard in clinical trials to minimise differences between the groups being compared and safeguard against bias. There is, however, a fear that such random allocation may not accord with patients' preferences for the intervention or treatment, thereby compromising trial validity. It is possible that patients may resent not receiving their treatment of choice, and their negative attitude may lead to non-adherence to treatment or affect outcomes in some other way. Consequently, one option for trial designers is to include patient preference arms, whereby patients with no treatment preference are randomly allocated to experimental and control arms, while patients expressing a treatment preference are allocated to receive their preferred treatment.