It seems like the reliability calculation on the gearbox is opposite that of the engine. Picking more gears causes a rise in reliability, I would think the less gears you have the more reliable the box as it would not require as many shifts and therefore less wear. When picking a valvetrain the less complex the better, but in the drivetrain a 4 speed manual is less reliable then a 8 speed dual clutch. Was this intentional?
It could be that the wear is spread across more gears so any one gear gets less wear compared to a 4 speed box? However, yes simplicity means there is less to go wrong.
More gears = more shifting. If you ask from me, I would say that the most wear on gearbox comes from shifting, and not when you are actually on the gear.
You’re partially correct… Shifting more often has the potential to wear out the gearbox synchromesh sooner but since each gear is used less often overall, the gear life is theoretically improved.
I suspect it is the quality bonus from the year that increases gearbox reliability in Automation; A 4 speed from the 70’s is, in both metallurgy and design, less reliable than one freshly made in 2014.
When I said 5 speed standard vs 8 dual clutch I was talking the same year, check yourself.