I always took it as him preferring typing on the white caps over the other ones; prefer the feel of pbt over what's used in the black (pom) and backlight (?).. Though I think I got that from other threads, maybe even geekhack.
Search shows a few things, but he'll be able to tell for sure
*"this thread isn't about backlight or not, this is about quality.
this noppoo is my 4th noppoo. I prefer the white one bcause of the very good PBT keycaps. The backlight one has the worst keycaps. " & "so good the white, so bad is the backlight noppoo.
the keycaps feels very glassy, hate that.
hrmpf, this could be my last noppoo. " @ noppoo backlit
*nominates choc mini white caps @ caps of 2011
So, sorry for jumping the gun on you