Yes. Nobody has come up with a better name for it yet.
In the case of 15/20 minute lessons, I think "Ripp Off" would fit the bill, as well as being almost impossible for the instructor to manage.
within the plethora of rules about qualifying for a UK PPL?
This raises some interesting points as training for a PPL can only be conducted at an ATO/RF however; legally, an FI could give a lesson, but it may be that it would no longer qualify towards the issue of a licence if it was outside such an organisation.