Once upon a time, in fact until the 30th June this year, on a UK NPPL the SEP class rating existed. It then became a requirement for all NPPL holders to go through a paperwork exercise and have SSEA with a rolling 2 year period.
There are many people out there who had NPPL licenses and had an SEP rating added to them after holding a Microlight rating and vice versa and all the ealry ones were issued by the NPPL Group/CAA with and SEP rating not an SSEA rating.
Stick that in your pipe and smoke it.