How is Draft Coach different to making draft submissions through Moodle?
Answer
Firstly, Draft Coach is a completely separate tool from making draft submissions through Moodle (as per this FAQ), the purpose of Draft Coach is that students can check their Similarity score (as well as grammar and citations) without having to make a Moodle submission. Therefore, when you run a Similarity Check on Draft Coach it is all contained within your document and there is no submission being made.
Of course, because Draft Coach runs outside of Moodle you can choose to use both the Similarity Checker within Draft Coach as well as making draft submissions through Moodle.