"I only ask because it never used to be like that in the MCDU database, I always recall them being identical until the last few months."
What sort of plane are we talking about here, Scallywag? As a 747-400 maintenance engineer, I set up the default values on the FMC MAINT Perf Factors page after I've updated the Nav Database (every 28 days). If the values have changed and you haven't been told about it, perhaps your Maintenance dept. have stuffed up? Do you have a list of default values in your manuals/Tech Log.
From memory, the values return to the defaults at the end of the flight, but I'll have to confirm this.
Rgds.
Q.