Often, elements that one wishes to transform are not aligned with the canvas. In these instances, using free transform will diagonally distort the object. Current workarounds include rotating the object to align with the canvas before transforming its dimensions (not ideal since it adds an extra unneeded instance of reprocessing the pixels, damaging image quality), and finagling things with other transform modes (not ideal because this is a slower, more involved process than the proposed feature).
Manual adjustment and rotation of the transform bounding box would be a useful addition to the transform tool.
I know it’s a cardinal sin around here to do this, but when a clear example already exists in lieu of a mockup (that takes time to produce and really doesn’t even need to be made), I will refer to it. Example of desired feature: How to adjust the Transform Bounding Box in Procreate - YouTube