PreArm checks: Gyro bias

I’m wondering why gyro bias learned is not included in EKF pre-arm checks, additionally to tilt & yaw aligned?
It seems to be of similar importance as it’s required by EKF to start fusing almost every sensor - GPS (for copter), optical flow, body odometry, range beacons.

But here only tilt and yaw alignment are required for EKF to report healthy attitude.
While in copter INS arming checks gyro biases are explicitly mentioned.

Is it bcz gyro bias learning takes longer (~30sec) than aligning tilt & yaw (seconds)?