You could kind of relate this to a Photographer.
If you hire him to shoot your wedding...he does the work.
the Negatives belong to HIM. The Proofs belong to HIM.
The Photographs belong to HIM. That is, until you purchase them.
The same applies here...
If you ordered JUST a mixed song, that is ALL you get.
You will NOT get each individual track, the effects chains he used,
or anything else. You will get a completed MIX. It won't even be
mastered, as that is an entirely separate process.
As the saying goes....you get what you pay for.