just checked the Arkefly website, they have 2 different longhaul config's, one for B763 (so their legacy aircraft) and one for B763Winglet (so YI)
Star Class has more legroom than their new Premium class, thus I think its safe to say they've not touched the config since it left TOM
As you say Thomsonfly offered "extra" seats, which is purely because the front cabin (ie between doors 1 and 2) is split partly Premium and partly standard but the result of that is those 4 or 5 row have more legroom but a standard seat.
Thomson Airways don't sell that any more with only 1 or 2 Thomsonfly aircraft operating longhaul the rest being legacy FC aircraft, where the while front cabin is Premium