I'm not sure whether or not this will effect things, but there is a difference on the JSON Data tab between a 'legit' Legacy grant and a Legacy granted using this tool. The 'legit' ones end with a 'z' on their earned date while this isn't currently appending the 'z' to the "PrestigeEarnedDates" listings.
Just thought I'd let you know so that if this is an oversight it could be corrected. Otherwise, I'd caution people about using this tool to give Legacy items since there is a way of identifying what has been hacked versus what hasn't.