include-transitive-objc-categories not working for NSURL categories

[stuartmorgan]

I was missing some NSURL methods, and found that they were in a category in NSURL.h. Based on this comment and the description of #1690 I expected them to automatically be there:

name: FoundationPathProvider
description: Bindings for NSFileManager.
language: objc
output:
  bindings: 'lib/src/ffi_bindings.dart'
headers:
  entry-points:
    - '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h'
exclude-all-by-default: true
objc-interfaces:
  include:
    - 'NSBundle'
    - 'NSFileManager'
    - 'NSURL'

They were not, however (using ffigen 16.0.0). I tried adding include-transitive-objc-categories: true explicitly, and that didn't help. But when I added

objc-categories:
  include:
    - 'NSURLPathUtilities'

they showed up. I would not expect that to be necessary.