$props() rune does not replace all usages of export let

[Tortoaster]

Describe the bug

Svelte 5's new $props() rune does not retrieve data from the load function of +page.[js|ts]. This might be intended, but it's not immediately clear to me after reading the documentation. It's a nuisance because using export let for this purpose disallows using runes anywhere else in the page.

Reproduction

Given the following +page.js:

export async function load() {
    return { message: ':)' };
}

This +page.svelte works as expected (renders :)):

<script>
    export let data;
</script>

<div>
    {data.message ?? ':('}
</div>

However, the equivalent (?) Svelte 5 version does not:

-    export let data;
+    let data = $props();

Output: :(

Logs

No response

System Info

System:
    OS: Linux 6.8 Ubuntu 22.04.5 LTS 22.04.5 LTS (Jammy Jellyfish)
    CPU: (24) x64 AMD Ryzen 9 7900X 12-Core Processor
    Memory: 19.74 GB / 30.50 GB
    Container: Yes
    Shell: 5.1.16 - /bin/bash
  Binaries:
    Node: 22.3.0 - ~/.nvm/versions/node/v22.3.0/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v22.3.0/bin/yarn
    npm: 10.8.3 - ~/.nvm/versions/node/v22.3.0/bin/npm
    pnpm: 9.7.0 - ~/.nvm/versions/node/v22.3.0/bin/pnpm
    bun: 1.1.20 - ~/.bun/bin/bun
  Browsers:
    Chrome: 129.0.6668.100
  npmPackages:
    svelte: ^5.0.0-next.1 => 5.0.0-next.264

Severity

annoyance

[Conduitry]

The prop is called data, so the equivalent in Svelte 5 is let { data } = $props().