There is no rule that there has to be a single payment per authorization, if you read for example mastercard API https://in.gateway.mastercard.com/api/documentation/integrat... it says you can partially capture, you can extend authorization. So for all you know when you buy at amazon it just updates the authorization and charges you later but keeps authorization going and amazon might just check if they have auth token for your card and if they do system allows you to continue and to you it seems instant.