Page is remounted when params change in (optional) catch all routes

Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/dreamy-firefly-4nsplp

To Reproduce

Start the provided application https://codesandbox.io/p/devbox/dreamy-firefly-4nsplp

click + link
loading page is triggered
locale state is reseted

Current vs. Expected behavior

It looks like the page is remounted, but I actually expected the page to be the same, with changing props. Keeping local state and not triggering the loading page.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Sun Aug  6 20:05:33 UTC 2023
  Available memory (MB): 4102
  Available CPU cores: 2
Binaries:
  Node: 20.9.0
  npm: 9.8.1
  Yarn: 1.22.19
  pnpm: 8.10.2
Relevant Packages:
  next: 15.0.0-canary.25 // Latest available version is detected (15.0.0-canary.25).
  eslint-config-next: N/A
  react: 19.0.0-rc.0
  react-dom: 19.0.0-rc.0
  typescript: 5.3.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Navigation

Which stage(s) are affected? (Select all that apply)

next dev (local), next start (local)

Additional context

The change in behaviour was introduced in https://github.com/vercel/next.js/releases/tag/v14.3.0-canary.27 and still exists in the latest canary.

I suspect that the behavior was introduced in https://github.com/vercel/next.js/pull/65063

When using parallel routes with a catch all segment on the main route it will retrigger loading boundaries when navigation is only relevant for the parallel route slot.

vercel / next.js

Page is remounted when params change in (optional) catch all routes #66751