What does ReqnrollCodeBehindOutputPath do? (strange behavior)

[myfero]

I am facing very strange behavior with this property. I was looking for a way to generate test code out of feature files that are lying outside of project and I found that property in Reqnroll.Tools.MsBuild.Generation.targets.

I have following structure

solutionDir
   testProject
      testProject.csproj
   Specification
      Features (with feature files and nested structure)

Now I am using following csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <ReqnrollCodeBehindOutputPath>s</ReqnrollCodeBehindOutputPath>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
    
    <PackageReference Include="Reqnroll.xUnit" Version="2.4.1" />
    <PackageReference Include="xunit" Version="2.8.1" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
    <PrivateAssets>all</PrivateAssets>
        <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="FluentAssertions" Version="6.12.0" />
  </ItemGroup>
  <ItemGroup>
    <ReqnrollFeatureFiles Include="..\Specification\Features\**\*.feature" >
      <!--<CodeBehindFile>Features\%(RecursiveDir)\%(Filename).feature$(DefaultLanguageSourceExtension)</CodeBehindFile>-->
      </ReqnrollFeatureFiles>    
  </ItemGroup>
  <!--<ItemGroup>
    <None Include="..\Specification\Features\**\*.feature">
      <Link>Specification\Features\%(RecursiveDir)%(Filename)%(Extension)</Link>
    </None>
  </ItemGroup>-->
</Project>

Now where it gets interesting. If ReqnrollCodeBehindOutputPath is empty or doesn't exist in csproj then .feature.cs file is being generated in 'solutionDir\Specification\Features**.feature.cs'
But if it has ANY value then feature file is generated inside project, in 'solutionDir\testProject\Specification\Features***.feature.cs'

Don't get me wrong, it being spawned in the project location is quite success for me and quite satisfying for what I want to achieve. I was just wondering if this is bug, coincidence (?) or desired behavior. If it is a bug, should I look for another way to generate test/designer files in desired location?

Thanks in advance :)