Ah, figured it out myself. Looks like you just need to add the element and it will work correctly. For future reference my request would then look like
curl -u username:password -v -X POST -H “Content-type: text/xml” -d “
myStoreTestRPFTOCtrueacmefile://C:\myData\test.TOC” “http://localhost:8080/geoserver/rest/workspaces/acme/coveragestores?configure=all”
Sorry for the trouble.