Yeah. That’s a different feature request which has also been ignored for years. (The ability to constrain the cropping box to active image area so there is no black in the corners.). Anyway the change in 6.6 is a similar capability for the distortion correction. (Though implemented a little differently than would be required for cropping. But anyway that’s outside the scope of this post.
Vote and discuss here if you’re interested in that:
https://forum.dxo.com/t/crop-tool-limit-to-rotated-picture-area
Note despite how simple this would be to implement this was requested SIX years ago so don’t hold your breath.