Paket pack multitargeting doesnt create separate groups of dependencies per fw

Description

Paket pack multitargeting doesnt create separate dependency groups per framework.

Repro steps

Use groups to setup different version restrictions per framework for a project

group net452-build
    framework: net452
    redirects: off
    source https://api.nuget.org/v3/index.json
    nuget Restsharp ~> 105
    nuget Newtonsoft.Json >= 8.0 lowest_matching: true

group netstandard-build
    framework: netstandard20
    redirects: off
    source https://api.nuget.org/v3/index.json
    nuget Restsharp ~> 106
    nuget Newtonsoft.Json >= 11.0 lowest_matching: true

group net452-build
    Restsharp
    Newtonsoft.Json

group netstandard-build
    Restsharp
    Newtonsoft.Json

Expected behavior

Nuget package is generated with one set of dependencies for net452 and another for netstandard2.0 with different restrictions according to groups above

Actual behavior

Paket generates a single dependency group for all frameworks tries to unify (?) the version requirements from my groups.

Known workarounds

None

Start by reproducing the issue with the shown Paket groups and the paket pack command, then inspect the generated NuGet package's dependency groups for net452 and netstandard20. Done means the package preserves separate dependency restrictions for each framework instead of unifying them; the payload names no source file or test to begin with.