Isuzu Option Codes Same As GM's Codes?

Out of curiosity, I looked up the Option Codes on my '95 Rodeo. One of the codes was G80 - Limited Slip Differential. This caught my attention because G80 was also the option code for the same option on my old '87 Buick Grand National (a low 12-second daily driver, by the way.) I checked a few other codes on the Rodeo and found they were the same as GM's. Obviously, Isuzu and GM share some or all of their option codes (or RPO codes as GM calls them.) Anybody know the story behind this?

Alot of Isuzus option codes are GM codes. This is from GM owning Isuzu for so long. Who knows if that will stay the same if Isuzu ever comes out with their own vehicles again now that GM sold off their shares.