Update

I called Murff's  after I posted yesterday's story - probably should have called them first, but the weren't open yet.
They told me:

• They actually remove about an inch of soil each time they harvest.
• They harvest grass somewhere every day, and may harvest the same spot once or twice in a year.
• They do not haul in dirt.
• Finally, she had no idea why they haven't dug themselves into a hole.