This all stems from the complete nonsense EASA has made with regard to acceptance of flight time in Annex 1 aircraft.
Back in 2014, the intention was that flight time in Annex 1 (a) - (e) aircraft could be counted towards SEP revalidation. As the legal cogs slowly ground away in EASA, evntually that was agreed...
But at no time was the intention that such flight time could ONLY be used for that purpose!
Meanwhile, a different EASA group looked at the use of Annex 1 (a) - (d) aircraft for flight instruction - eventually this was agreed; Annex 1(e) aircraft ('microlights') could NOT be used for this purpose.
There are some idiots now at EASA who cannot understand that it is quite OK to do a PPL course on something like a Piper Cub, including the Skill Test (assuming the examiner is happy). One such person even thought that the FI who taught on a non-EASA aircraft could count the hours towards his/her SEP Class Rating revalidation, but NOT towards his/her FI certificate revlidation....Where do they find these people?? There was even a suggestion that a pilot would have to keep EASA and non-EASA flight time in separate log books.
Anyway, as far as the UK is concerned you can use flight time in non-EASA 'annex 1 (a)-(d)' aircraft for training on anything issued by the CAA (provided that the aircraft has been deemed to be OK by the CAA) and it will also count towards revalidation. Annex 1(e) 3-axis microlight flight time can be used for revalidation, but not for the refresher training flying requirements.
To resolve this utter dog's breakfast, AOPA (UK) drafted an AltMoC for the CAA to pass to the DfT; however, due to the UK/EU exit situation that had to be shelved. The draft AltMoC was sent to IAOPA and any national AOPA is welcome to submit it to their NAA.
When the UK leaves EASA, the problem will go away in the UK as we won't have 'EASA' and 'non-EASA' aircraft any more.