Losing sign of quaternion

[Yaxit]

Could someone please explain what is the output of the SFLP quaternion block?
I see three half-floats are generated, and the fourth component is inferred from the game rotation being normalized.
Is the fourth component the real part? Don't we lose the sign with this transformation?

STMems_Standard_C_drivers/lsm6dsv16bx_STdC/examples/lsm6dsv16bx_sensor_fusion.c

Line 182 in 8d7095f

static void sflp2q(float quat[4], uint16_t sflp[3])