Pay-in-30 and pay-monthly, assessed against pay-in-four
The category's other two shapes: defer everything for a month, or spread it over many. Assessed on how differently they behave when something goes wrong.
Instalments
The pay-in-four plan, assessed as a credit product
Four instalments, no interest, one checkout tap. Assessed on the terms rather than the button — because an instalment plan is credit whatever the button calls it.