As a bit of a heretic when it comes to the current print group thinking, I'll take a try at that.
The first and most important point is that for the most part, we all respect each others work and ideas. None of the current or future things we believe or know about the cards production would be possible without all those people laying the groundwork, and or adding information. That's not to say we don't occasionally have some serious disagreements, but that's the nature of things.
To me, the current print groups are sort of like a good intro to the complexity of the set. It's complex enough to be a bit of a challenge, but not so complex that most people can't grasp it.
One of my favorite catalogues in a different hobby is set up where for complex sets they show the basic set with the truly major varieties. Then there's a listing that lists different papers, gums etc along with a usually extensive listing of plate flaws that are collectible. And on occasion, they follow that up with a note that's polite but should read "if you're truly insane and have to know literally every small detail of this set you should buy this book by someone crazier"
That gives the collector a framework of how far to specialize.
In that way, the print groups are a solid foundation for further investigation. As well as a good framework for a collector to decide when to stop.
Where it breaks down is perhaps well into crazy land.
Within the current framework-
I would call the dozen or so 150 only cards print group 1.
And the rest of the 150s as either print group 2 or maybe 1A
Within the 150 group, there were at least three individual printings. As maybe the most obvious example, the Tinker hands on knees comes at least three different ways, each would have required a change to the original art, and new masters/transfers/etc.
Chicago partly visible behind Cubs
Chicago semi removed
Chicago not there at all
So that makes it at a minimum
Group 1 - 150 only, and potential sheetmates which may or may not be identifiable or have even existed at all.
Group 2- 150 but from the sheet that produced the Tinker with clear Chicago
Group 2A - 150 from sheets that produced tinker with partly removed Chicago
group 2B- 150 from sheets that produced correct cards with fewer design flaws.
And here's where there's a major branching
I consider 350s to be an entirely new set.
There are a few cards that show design changes between 150 and 350. Most are very minor. But also would have required new masters etc.
And within the 350's?
At least three more divisions.
If you want a "missing red" card, just find a Dygert without lipstick. They're common enough that I don't believe they're errors. They're readily available both with and without. And have a few cards with the same stuff going on but less obvious.
Hopefully the 350-460s and 460 only groups have fewer divisions, but I'm expecting them to be at least two each.
The other big branching spot is
were the same sheets used for all backs? Or did individual brands use their own sheet layouts and player selection?
UGH...... Since there's a couple team variations in the 350's that are only on PB, it can be pretty much assumed that at least partly brands may have had different sheet layouts and even different sheet sizes. That's both good and bad. On the bad side, it makes things 15x as complicated.
On the good side, it explains reasonably well why groups of 12 or groups of 17/34 both exist.
Confused yet?
Yes, for the vast majority of collectors, print groups as we currently explain them are just about right. And we have a few people who did some great work with access to lots of cards over several years to thank for that semi comfortable station we can stop or rest at before transferring to the crazy train lines.