Thanks manymak, however I read that differently to you.
I read 61.375 as 'if you did your PPL test in a twin you would get MEA and you would also be allowed to fly SEA as an extension.'
But I can't find anything that absolves you from having to complete a SEA review if you have a current MEA review as per 61.475.
I'm usually pretty good at this air law business but Part 61 has me stuffed.