OK, see what you mean - the rating is included in the licence by virtue of schedule 8 but the requirement to have the rating valid is elsewhere.
This I expect could then allow training to be conducted at an unlicensed airfield. However, how many FTOs or RTFs have approval for SEP or MEP flight training at unlicensed airfields?
Following an accident it would be vary hard to stand up and say that it was safe to send a student solo at an unlicensed airfield when the CAA has clearly indicated that they consider such actions to fail in meeting the minimum safety standard requirements. Duty of care may be a factor especially when it is not part of the required training to complete any solo flights.
Regards,
DFC