the ADL has always been the utility gun. BDL is the one that was made into the classic rifle- cut checkering, floorplate magazine, white line and black fore end with black grip cap and butt plate, gloss wood, so forth. It was what old fashioned shooters wanted in a fancy rifle.
The CDL was originally classic, IIRC, not custom. It basically went with the BDL and used less fancy stuff. Matte finish, no forend or grip cap, so forth.
This is what they have meant in general over the past 40-50 years.
The ADL, in years past, was one fugly weapon. Stamped checkering, lousy wood, so forth. I'm almost happy to see plastic stocks instead of that