Not adding NET_STANDARD_2_0 define

How to reproduce:
1. Open the attached "New Unity Project.zip" project
2. Switch to UWP
3. Select .NET Standard 2.0 Scripting backend in Player settings
4. In Project window select Packages > Microsoft.Extensions.DependencyInjection > Microsoft.Extensions.DependencyInjection.dll
5. See define constraints in Inspector window showing "define constraint is incompatible" error
6. Open "Assembly-CSharp.csproj" file with a text editor
7. Search for .NET version in DefineConstants line

Expected result: "NET_STANDARD_2_0" constraint is present
Actual result: "NET_4_6" constraint is present

Reproducible with: 2018.4.35f1, 2019.4.27f1, 2020.3.9f1, 2021.1.8f1, 2021.2.0a17

Notes:

• Not reproducible on Standalone