The behavior of any default bias is to be parallel to an imaginary line between the next and previous CP on the spline. Bias alpha and gamma adjustments are like offsets from that imaginary line.
If the next or previous CP is moved across that line, a non default alpha or gamma bias will flip to maintain the same offset to the imaginary line as before.
However, that is only in the modeler, where you do want the bias to truly represent its offset to the imaginary line.
Bias "flipping" (if that's what we are talking about) is normal in the modeler, but is prevented from happening in animation. If there is a case where biases flip in animation that would be something to look at here.
To avoid annoying bias flipping in the modeler, do bias adjustments last in your workflow, after you are fairly certain your CPs are as best placed as they can be.