As far as I understand, Unity strives to provide a consistent degree-based API. That's why Quaternion.AxisAngle (taking its angle in radians) was deprecated in favor of Quaternion.AngleAxis (which takes degrees). There is nothing wrong with degrees per se, but a lot of computations are naturally done in radians; if this is the case, the programmer is forced to convert their result to degrees just for Quaternion class to immediately convert it back to radians. This means two unnecessary floating-point multiplications which give nothing but performance and precision loss.
Of course, having both AxisAngle and AngleAxis is misleading. But how about AngleAxisRad?