After some more experimentation, I am happy to say that I found the cause of the jaggies in the LR processed RAW image.
I dragged the sharpen slider from its default setting of 25 down to zero, then reprocessed the file. The LR image now matches the ACR image nearly 100%.
I'm amazed that a 25% setting could make that much difference. If you want to avoid sharpening artifacts in your LR processed RAW images, and you don't want to sharpen in another program after the fact, I suggest some experimentation with this tool, as it has profound effect, to say the least!
Then this may well be the cropping bug. The default shouldn't have that much effect. The default should look quite similar to ACR. I also noticed you have some color aliasing. What setting did you use for the Denoise parameter? The default of 25 is relatively high, and should certainly be able to deal with the color-aliasing.