Interesting 1990 CMC/ProCards Minor League Sheet
 

This appears to be a sheet that was printed for the team sets (Green Backs) and not for the 1990 CMC AAA/ProCards A & AA Packs. All the ProCards are blank backed, don't know if it was an error at the time as someone forgot to have the backs for the ProcCards printed at the same time or just a progressive print sheet.

Fascinating! I wonder what thought process led to printing the AA and AAA sets on the same sheet. It would make sense for the pack-issued set, but seems like it would make collation of the team sets a real pain.

Agreed that’s what I’m trying to figure out, their reasoning and the contractor who printed the sheets

I am doubting this was the final production process. As the backs are incomplete it was likely a pre-production sample to show what the completed cards and quality would be. The remaining backs were unlikely to have been completed by the designers at the time and were not added.

These would have been provided to the company by the printer to show they can indeed create the product to satisfactory standards per contract or to get the contract. Probably plenty of extras in the sample run and employees took a few.

I also think pre production.

Not only proving ability, but for final final design approval as a last chance to catch things like bad words written on bats or getting the wrong guys picture on the card.
There may be tiny differences.

Putting up the sets may not have been the nuisance it seems. If the cutting was done manually, there would have been large stacks of each card, and putting the different sets in different places would be pretty easy.
With some automated system, it would be different, maybe easier, maybe harder, I don't know (That organization /collation stuff was a trade secret. )