I am not 100% sure on this, but the reason the right hand side has new skin is due to the replacement of the 'Static Pressure' ports. As smoke and debris contamination may well have affected all of the ports on both sides it will likely be a requirement to replace the lot and the Air Data Modules they connect to. The static pressure is fed to units known as an ADIRU and SAARU and off to other aircraft users of static pressure such as cabin pressurisation controllers. All the data from both sides of the aircraft is continuously cross checked. Should an anomaly be found, the aircraft alerts the crew to the issue and it can mean certain functions of the flight instruments start to go a bit 'wonky'. Replacing and retesting the lot is a far safer bet, but no doubt means skin panels bring removed etc. The left hand damaged area also contains the 'negative pressure relief' valves which no doubt were also replaced. There is lot going on in that part of the fuselage, hence work would require full replacement of affected system components.