Behavor #1 makes sense, since the input is assumed to be radians, not degrees. The adjustment adds pi/2 if you're above jump tolerance, so that's fine.
What would be nice was if unwrap had a feature that allowed it to work on any kind of series, not simply on radian angles.
The jump tolerance is not sufficient to tell whether you have a series in radian, or degree, or any other kind, so there would need to be an additional input.
I had always assumed that the second behavior was the actual one, but never tested it out. A literal reading of the help file does indicate behavior #1. But that's not what one would ever want to do. As a simple example, consider doing an unwrapping in degrees
x = mod(0:30:720, 360)
y = unwrap(x,180)
obviously you would want y = 0:30:720, but instead you get ...
y =
Columns 1 through 7
0 30.0000 60.0000 90.0000 120.0000 150.0000 180.0000
Columns 8 through 14
210.0000 240.0000 270.0000 300.0000 330.0000 333.0088 363.0088
Columns 15 through 21
393.0088 423.0088 453.0088 483.0088 513.0088 543.0088 573.0088
Columns 22 through 25
603.0088 633.0088 663.0088 666.0176
which is wrong (y no longer corresponds to the same angle as x, which is the point of unwrap)
Can anyone give an example of when you would want behavior #1 (the current behavior?)