(going down a rabbit hole now. I think that's the right phrase)
There are loads of sites that offer grave digging services or equipment (e.g. [0]) although none mention hoes that I can see. However, I did find more about the use of hoes to actually dig holes (coming back to the original subject): [1]. How could I have forgotten about 'mattocks'.
It's possible that the word "hoe" is rarely written down in this context. I wasn't able to find "putlock" in this context on the web, although I found a blockchain protocol where the name clearly linked the words "grave" and "putlock"