It would appear that there is more to the story than what was reported. Smoke in the galley happens on a regular basis, usually from food residue left inside one of the ovens after improper cleaning. Once the source is identified, this should not be a cause for a return. However if the smoke is suspected to be electrical and comes from outside the ovens, then wasting time with a fuel dump does not seem to be a prudent course of action.
One scenario where the crew action would be logical is an identified electrical fault that was fixed by pulling a circuit breaker, leaving the aircraft without a functioning galley (and possibly other systems), not something one wishes to cope with on a 14 hour flight.