Regarding your......
" why were the sovereign 460 super-prints short-printed? "
I cannot say for sure. However, these super-prints are fundamentally 350-only subjects by virtue
of the fact that they are found with American Beauty 350 (frame) backs. Paradoxically, these six
cards are also 460-only subjects, since they were printed with most of the 460 series backs. They
have split personalities
Now, onward to your 2nd question......
" how much is actually known about the print process of this specific group? "
I can date the 460 series printing of this set to as early as the Spring/Summer of 1910 due to the
fact that Frank Smith (traded to Boston, Aug 1910) and Red Kleinow (traded to Boston, June 1910)
are not depicted in the 460 series of the Sovereign set. Both of these guys' cards reflect their trades
to Boston with all the other 460 series T-brands (indicating that those print runs occurred later than
the Summer of 1910).
Considering this....perhaps these super-prints were printed at the very tail end of the Sovereign 460
press run, and therefore received very limited printing.
TED Z