It's good that they do these experiments, as it shows risks regarding heavy metal toxicity.
Vermicompost obviously contains lots of earth microorganisms that live in symbiosis ("living together") with plants here on earth - getting nutrients from plants (mostly carbs produced via photosynthesis, light not being available under the soil) and also supplying nutrients (nitrogen, minerals etc. from inert soil, converted to a bio-available form that plants can utilize) and even water. No surprise here, foodweb is a known concept by now with many people interested in this.
But I don't know that it would be the most practical to ship vermicompost from earth in large and continuing quantities. It might be better to initially ship the earthworms themselves (or at least their eggs) as well as (organic) foodstuffs for the humans there. This could then serve to ramp up a growing population of earthworms on the moon. Should be obvious though that this will be in a sheltered environment, not on the exposed raw lunar surface - like with earth-origin humans and their earth-origin-crop plants. This would be a live ecosystem being constructed from the ground up, protected from a hostile environment - not inert or sterilized materials.
Having a colony of earthworms would allow the setup of a vermiponics system (~"aquaponics" using worm casting nutrients instead of dissolved salts) for growing food plants, using some inert substrate for a physical support structure for the plants - no dependence on a possibly toxic growth medium. Potatoes and other root crops are successfully grown here on earth, together with the customary leaf and fruit crops. After the food has been eaten and the waste passed out again, the worms can come into play again, to convert this back into compost, as has been done successfully here on earth with multiple wet or dry vermicomposting toilet systems.
One drawback with vermicomposting is the amount of time it may take - much less of a problem here on earth if you've got some space and a friendly environment. (This is one site I found via websearch that was quite interesting regarding construction, ramp-up and maintenance here on earth, gives some feel of what could be possible.)
Ironic that these little miracle workers considered for the moon are named "earth"worms.
I'm interested how the difference in gravity would influence them.