Amazon Pay API-v2 Sandbox simulation not redirecting to checkoutCancelUrl

Question

I have integrated Amazon Pay API -v2 button in my website. While using Sandbox simulation "Visa ending in 3064" with "BuyerCanceled reason code" Amazon hosted page is redirecting me to "checkoutResultReturnUrl" instead of "checkoutCancelUrl" even though providing "checkoutcancelUrl".

webCheckoutDetails: after using get checkout session API

{
    "checkoutReviewReturnUrl": "https://www.example.com:4200/checkout/review",
    "checkoutResultReturnUrl": "https://www.example.com:4200/checkout/success",
    "amazonPayRedirectUrl": "https://apay-us.amazon.com/checkout/processing?amazonCheckoutSessionId=bc1b9372-53ed-ec9eefc5188d",
    "authorizeResultReturnUrl": null,
    "checkoutCancelUrl": "https://www.example.com:4200/checkout/cancel"
}

can anyone explain why it it happening?