Green is a puzzle. I can't see a pattern to the stuff they reprinted. One issue of their incongruously-titled Atomic Comics was made up of stuff from the Wheeler-Nicholson days!
There IS a pattern to Green's choice of what to re-issue. It is based entirely on what older comic book material they could get their hands on for the lowest resulting net acquisition and net printing cost. In the later mid 1940s they happened upon a great bargain in old MLJ material in series that MLJ/Archie was no longer running. And in the late 1950s, they came upon a goodly amount of old Fox Features material, as well as some from Robert Farrell's lines, and Charlton (both regular Charlton and Comic Media), some as final art, some as printing plates, and some as bound inside pages of already printed (but as yet unsold) books. That was a similar method to that used by Israel Waldman's I.W. and super Comics, and Norlen Magazines, -buying up old printing stock or old printed comic book stock from going-out-of business distress sales, and sales of old warehouse stock.