Beyond the correct analysis of marketing-speak the market looks like contract phones are basically a "worse than payday loan" interest rate of a couple hundred bucks and couple year payback period. So you get a $500 phone at a cost of maybe $2000 over the course of the loan. The MVNO resellers mostly seem to go prepay, I know I paid $300 for my phone some time ago, but I only pay $22 per month for voice and psuedo-unlimited data so I'm pretty happy.
It is interesting that Amazon is kinda in between, kinda a subprime loan seller and kinda a phone service reseller, probably for financial reasons.
Amazon does seem to be financializing itself, they do push their credit card every time I buy. It is no great modification to drift sideways into phone loans.
In the long run I expect to see them continue to financialize themselves into perhaps subprime car loans (outright buy Car Max or a competitor?) and eventually home equity loans (to buy more stuff at Amazon) or home loans (complete with prime membership to help fill your house with trinkets from china)
So it makes sense as a grand strategy thing to move away from Amazon the book retailer and into Amazon the bank. Nobody in America can make a living doing anything but FIRE sector in the long run by intentional regulation, so they kinda have to do this.
I think you should generally be suspicious when a vendor tries to get you, the customer, to use the vendor's own internal jargon. As a customer, I shouldn't need to know your jargon; I don't give a shit about your internal policies and terms. If you're encouraging me to speak your unnatural language, you're probably trying to give me a false sense of security and savvy that makes it easier to pick my pocket.
One sees similar moves in many complicated transactions like real estate, automobile leases and purchases, etc.