Increasing the Bend Radius increases the Arc Length as well. How can this be explained?

The radius of the circle is directly related to the circumference. If you increase the radius, the required circumference (or arc length for partial circle) will also increase.

circumference = 2 * pi * radius

Thanks

Your part is related to the Angle of 48 Degrees, to shorten the bent portion you need to change the degree as well

Yeah...you are basically asking "Why does the circumference of my pipe increase when I increase it's diameter?". Because it has to.

The radius of the circle is directly related to the circumference. If you increase the radius, the required circumference (or arc length for partial circle) will also increase.

circumference = 2 * pi * radius