Flash of parent "loading.tsx" in parallel routes with dynamic folders

[mrjasonroy]

Link to the code that reproduces this issue

https://github.com/mrjasonroy/nextjs-14.1.1-parallel-route-loading-flash

To Reproduce

1. Clone Repository
2. Navigate Using the lefthand navigation to a non cached page
3. Observe flash of blue in the header from the loading.tsx in app/todo/loading.tsx

https://github.com/vercel/next.js/assets/603729/6a846189-3007-46bb-908d-758cdec80b0d

Current vs. Expected behavior

When visiting a dynamic route of todo/[id] only the loading.tsx content from app/todo/[id]/loading.tsx should be shows as content is being loaded, not the flash of loading.tsx content from the parent folder

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.1.0: Mon Oct  9 21:33:00 PDT 2023; root:xnu-10002.41.9~7/RELEASE_ARM64_T6031
Binaries:
  Node: 20.9.0
  npm: 10.1.0
  Yarn: N/A
  pnpm: 8.10.5
Relevant Packages:
  next: 14.1.1-canary.55 // Latest available version is detected (14.1.1-canary.55).
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: N/A
Next.js Config:
  output: N/A

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

App Router

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

next dev (local), next start (local)

Additional context

confirmed in dev and start