I am (well at least 99.9%)... and it is...
Bullykaka that is about increasing performance. I would now be VERY wary of anything that "Dealer person" tells you. IF there is a fault in the earthing on a vehicle ex factory then there will be a Service Bulletin and they will "add" the extra earth strap for Free.
The most common 'earthing' issue I am aware of that pops up from time to time is one in regards the Sub Tank fuel transfer pump and computer but that is like 1 in 100 vehicles and usually after a few years
P.S. No real biggy but when quoting model year rather than when you purchased the vehicle always use the Manuf Build Plate date (yours is prob a 2010) and if engine related IE is yours a ZD30 or Petrol apart from that yes, yours should be a Y61 Series 7