False positive with Rails/FilePath for a list of paths separated by colon including Rails.root

[tk0miya]

When I created a list of paths separated by colon (like $PATH envvar) including Rails.root, the Rails/FilePath cop warns to use Rails.root.join. But it's not appropriate in this case.

Expected behavior

No warning is emitted.

Actual behavior

$ bundle exec rubocop --require rubocop-rails
Inspecting 2 files
.C

Offenses:

test.rb:3:8: C: Rails/FilePath: Prefer Rails.root.join('path/to').
PATH = "#{Rails.root}:/path/to/directory"
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

2 files inspected, 1 offense detected

Steps to reproduce the problem

https://github.com/tk0miya/rubocop-rails-bugs is a minimal reproducible project.

RuboCop version

$ bundle exec rubocop --require rubocop-rails -Vbugs [master]
1.28.2 (using Parser 3.1.2.0, rubocop-ast 1.17.0, running on ruby 3.1.2 x86_64-darwin19)
  - rubocop-rails 2.14.2