Stepper motor torque constant and electrical constant
Here is a hybrid stepper spec that shows them being equal, as expected:
Insulation class: Class B.

Dielectric strength: 500VDC for one minute.
Insulation resistance: 100MΩMin., 500VDC.

Electrical Specifications:
Model:  86BLS98 .
Number of poles: 8.
Number of phase: 3.
Rated voltage(DC): 48V.
Rated speed: 3000RPM.
Rated torque:  1.4N.m/197.2oz.in.
Rated Power: 440W.
Peak Torque: 4.2N.m/591.5oz.in.
Peak current: 33A.
Resistance: 0.2 ohms.
Inductance: 0.48mH±20%.
Torque constant: 0.13 Nm/A.
Back E.M.F: 13.5 V/KRPM.
Rotor inertia: 1600 g.cm2
Body length: 98mm/3.9in.

0.13Nm/A  so \$K_T\$ = 0.13
13.5V/1000 RPM  so 13.5V/16.66 rotations/s or 105 rad/s so \$K_E\$ = 0.13 .
Could be a mistake in their data I guess.