iOS back motion inconsistency

Describe the bug

The back motion on iOS in dependent on the scroll position of the page you are currently on.

When on the very top of page A and going back from page A to page B, you will see page B below page A during the motion.
However, if you scroll page A down before doing the back motion then you will see a blank page below page A.

https://github.com/user-attachments/assets/830583e5-1d3a-493d-9456-e41af8f28ca1

Reproduction

On iOS device.

Create svelte demo project via:
https://svelte.dev/docs/kit/creating-a-project

Add this to package.json scripts:
"dev-phone": "vite dev --host "

1. Execute: npm run dev-phone
2. Navigate from Home to About through navbar
3. Execute back motion on iOS (works as expected)
4. Navigate from Home to About through navbar
5. Scroll to the bottom of about
6. Execute back motion on iOS (page below about is blank)

Logs

No response

System Info

Device:
iPhone 13
iOS 18.1.1
Safari

Severity

annoyance

Create the Svelte demo project using the linked project guide and add the package.json dev-phone script. Reproduce the back motion on an iPhone 13 with Safari both at the top of About and after scrolling to its bottom. Trace the navigation behavior from the Home-to-About reproduction; done means the page below About is rendered consistently during back motion in both cases.