Never has so much waffle been written by so many.....
Fact is Gulfstream have to place the galley at the back to save the loss of two windows in the cabin (hidden by the galley and place the pax further from the noise (engines). (It is dark - your pics are clever photography)
The Crew are self-contained in the forward galley with the toilet all in one section.
As for smells I think the G550 crew toilet is likely to be more smelly after a Bombay curry. No rest there.... come on wake up smell the coffee.
AND the person who is important is the owner - not the F/A wanting to store food in cabin which cant be open at 450FL or above either.
Resale is also important - forward galleys are sort after, aft are not.
Remember the G550 is still a re-engine G1 which had propellers I recall. Check the Type Certificate if you want.