Mike,
Actually think it's working. To load values to eeprom after a MPU9250 Library calibration (following 'a', 'g', or 'm') you use the 'l' command instead of the 'e' command. The 'e' command is for loading static cal values into eeprom. It's a bit confusing, but a bit challenging without an easier GUI!
Here's what I see doing an 'a' cal followed by an 'l' load command:
Teensy Accel and Gyro EEPROM Biases:
Current Accel Biases (mss) and Scale Factors:
0.000000, 1.000000
0.000000, 1.000000
0.000000, 1.000000
Current Mag Biases (uT) and Scale Factors:
0.000000, 1.000000
0.000000, 1.000000
0.000000, 1.000000
IMU Biases:
Accel X Bias: 0.071219
Accel X Scale Factor: 1.001855
Accel Y Bias: 0.477212
Accel Y Scale Factor: 0.999564
Accel Z Bias: -0.165475
Accel Z Scale Factor: 1.010679
Gyro X Bias: 0.000000
Gyro Y Bias: 0.000000
Gyro Z Bias: 0.000000
Mag X Bias: 0.000000
Mag X Scale Factor: 1.000000
Mag Y Bias: 0.000000
Mag Y Scale Factor: 1.000000
Mag Z Bias: 0.000000
Mag Z Scale Factor: 1.000000
Static Calibration Values Saved to EEPROM
MPU9250 Lib Calibration Values Saved to EEPROM
Teensy Accel and Gyro EEPROM Biases:
Current Accel Biases (mss) and Scale Factors:
0.071219, 1.001855
0.477212, 0.999564
-0.165475, 1.010679
Current Mag Biases (uT) and Scale Factors:
0.000000, 1.000000
0.000000, 1.000000
0.000000, 1.000000