Deciphering Views SQL
how table aliases are created in joins is pretty simple - to have unique alias views takes names of both tables and combines them.
you can check more simple example:

SELECT node.created AS node_created, node.nid AS nid, users_node.mail AS users_node_mail
FROM 
{node} node
LEFT JOIN {users} users_node ON node.uid = users_node.uid


users table is joined to node table and unique name becomes "users_node". For files table it would files_node. 

I think it is the only way to have unique aliases. Also it is easy to understand from which join data is coming