to clarify: torrents are marked "edu" if the user has a .edu address, this makes those torrents stand out. The majority of non us universities do not offer *.edu addresses to their staff and students.
Yes, you're right. Which then brings up the question about how to determine if the data comes from an "academic" address, as was pointed out, only US institutions or institutions which are accredited by the US Dept. of Education can apply for an .edu top level domain— meaning nobody has it.