Just thought this was a little strange.

I opened a new in box RD-7900, bolted it on, no cable yet.

the High limit screw came about half way backed out from the factory. and it is sitting below the 4th cog. I had to back out a few more turns to get it to sit on the smallest cog. The hanger is not bent.

Is this quite normal? On SRAM I could only get to 2nd cog with the screw turned in. My guess is Shimano thinks if my shifter or cable broke, I can select probably any gear to ride home.

More range means the rear derailleur can accomodate a variety of dropout thicknesses, but presumably SRAM has enough and Shimano's is overkill.

Maybe it is for juniors and cadets so they can block out the big gears easily?

typically, shimano derailleurs arrive out of the box with the limit screws set about two gears in- 3rd hardest and 3rd easiest. so yours is within reason.