When transforming an object for example to see how much transformation is needed compared to the sketch from the client. I need to move the transformation object to the side and then undo too see the difference in scale. When pressing apple-z twice the transformation is set to where I started the process and I need to start over. This has never been the case in earlier versions of Photoshop.
If you leave legacy off, undo is actually remembering more than one state inside of transform using Cmd Z to undo each step and Cmd Shift Z to redo each step - which is a lot more powerful than what was possible in prior versions of Photoshop. I see how Legacy isn't working correctly in the modal transform state - I've asked engineering to take a look.