I wouldn't necessarily disagree with you. However, what's the point of pumping grease into the same place via two different routes? One might as well ignore the nipples or zerks on top of the kingpin and use the ones directly on the stub axle.
Grease has been known to congeal and block the oilway in the kingpin. It was designed as an oilway and is therefore a small diameter.
Anyway, as you say John, each to their own. I suspect that owners are more likely to over-grease and therefore any difference in wear is likely to be minimal. Just don't let enthusiasm and over-use cause the grease to contaminate the brake disks and pads!
