I'm used to the term being used by old school computer scientists... i.e. to grok something is to know it very deeply, inside and out. I think the term may have originated in the sci-fi world w/ Heinlein. I got into the computer world about 20 years ago, but have read extensively about the history of the industry and the geek world I work and live in.
As far as grokable kits, I've been tempted to get the RoG bus... not sure when I'd build it, it would probably go to a storage unit with my other 1500 or so unbuilts.
My RoG BMW 7 series and Merc 560SEL and Fujimi Enthusiast series Ferraris are fun to just sit and grok.
I'm not into large scale kits, but I would love to grok the parts trees and instructions of Tamiya F1 kits and their large Lola and others..