Having looked at the seat maps for both aircraft I can see that on the 777-200 there is a better loo layout since F has one dedicated one at the front of the cabin.

And it is possible to do it on a 777-300 because I have been an a Turkish Airlines one - and the front F loo was big enough to swing two cats! And behind the F cabin there are 4 loos. So this means that the 8 people in F have immediate access to 5 loos - which is pretty impressive!