I tested a working version of the script and CBS test record with a wide variety of cartridges, MC, MM, $11 special, one with a bent cantilever, one supposedly incompatible with my tonearm, V15VMR. Basically, I tried to throw the book at them. I figured I would share some early results for the sake of curiosity.
NOTE: THESE ARE ONLY FOR TESTING PURPOSES.
I think that they can show why the initial script--rightfully--started at 1000Hz. Simply, as was reasoned, cartridges behave similarly below 1000Hz. The differences here are less than 0.5 dB in most cases. The hump from around 200-800Hz is due to the CBS test record (and, as in my previous measurements, the switch at 5kHz and messiness around 17kHz is also the test record). Differences below 50Hz may have to do with tonearm influence. (I will be testing Denon's classic Dynamic Servo tonearm to see if it helps with resonances if I can. This record may not go low enough to show anything conclusive.) The one that stands out belongs to a beloved line of cartridges. I want to confirm that result by testing a second cartridge but it seems to make sense to me. (Their headphones are also weird.)