Parallel, intercepted catchall routes provided wrong params

Link to the code that reproduces this issue

https://github.com/Drewsapple/repro-intercept-catchall

To Reproduce

1. Start the app (next dev or next build && next start)
2. navigate to /reproduction
3. click the link to /reproduction/double/double
4. refresh the page or otherwise load the same route so navigation is not intercepted

Current vs. Expected behavior

When the default export from (.)[...catchall]/page.tsx is loaded, the params object passed is are follows:

Navigating to /reproduction/single

{"catchall":["single"]}

Navigating to /reproduction/double/double

{"catchall":["doubledouble"]}

Instead of the route segments being concatenated as strings, they should be concatenated as array elements, i.e.

{"catchall":["double","double"]}

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Debian 6.11.6-1 (2024-11-04)
  Available memory (MB): 15748
  Available CPU cores: 8
Binaries:
  Node: 20.11.1
  npm: 10.9.0
  Yarn: N/A
  pnpm: 9.14.2
Relevant Packages:
  next: 14.2.18 // An outdated version detected (latest is 15.0.3), upgrade is highly recommended!
  eslint-config-next: N/A
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.6.3
Next.js Config:
  output: N/A

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

Parallel & Intercepting Routes

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

next dev (local), next start (local)

Additional context

I tried this in v14.2.14 as well, to see if it was a regression introduced by #65063 in v14.2.15, but the behavior was the same.

In v15.0.3 (with awaited params), the catchall group doesn't intercept a navigation with multiple path segments at all. This modification is tracked in the v15.0.3 branch of the reproduction repo.

Start with the linked reproduction repository and its (.)[...catchall]/page.tsx route, then run the documented navigation and refresh steps under the affected Next.js versions. Compare intercepted and directly loaded /reproduction/double/double params; done means both paths provide {"catchall":["double","double"]} while preserving the single-segment behavior.