This is my rough understanding of the subject (if I am wrong here, please correct me)

The "payment method" does not necessarily infer it is a "loan". The reason some lenders call it a "loan" is because they are backed by an FDIC-insured bank that allows them to charge whatever rates they please (essentially a loophole around usury laws). Once you become FDIC-Insured (think BofI, Webbank, etc) you are allowed to dictate what rates are reasonable and legal to charge to a business.

A merchant cash advance is just a sale of future receivables, with a unique collection method.