.net standard 2 does not seem to be included

Description

Please provide a succinct description of your issue.

Repro steps

Please provide the steps required to reproduce the problem

1. Open a solution in vscode with omnisharp

2. packet.dependencies

source https://api.nuget.org/v3/index.json

storage: none
framework: netcore3.1, netstandard2.0, netstandard2.1

nuget Akka
nuget Akka.Logger.Serilog
nuget coverlet.collector
nuget dapper
nuget Microsoft.Data.SqlClient
nuget Microsoft.Data.Sqlite
nuget Microsoft.Extensions.Hosting.WindowsServices
nuget Microsoft.NET.Test.Sdk
nuget MSTest.TestAdapter
nuget MSTest.TestFramework
nuget polly
nuget Serilog.AspNetCore

1. Message will pop up automatically "There are unresolved dependencies. Please execute the restore command to continue."

2. Check omnisharp logs:

[warn]: OmniSharp.MSBuild.PackageDependencyChecker
        g_service: Did not find 'NETStandard.Library' in lock file.
[warn]: OmniSharp.MSBuild.PackageDependencyChecker
        g_test: Found package reference 'NETStandard.Library', but none of the versions in the lock file ("1.6.1") satisfy [2.0.3, )

If possible then please create a git repository with a repro sample or attach a zip to the issue.

Expected behavior

I guess I expect it to not give these warning - I did not specify .net standard 1.6 anywhere and 2 and 2.1 is explicitly stated in packet.dependencies

Actual behavior

I get the warnings above and vscode keeps telling me that some dependencies are missing - if I run dotnet restore I get All projects are up-to-date for restore.

Start with the packet.dependencies example and the OmniSharp PackageDependencyChecker warnings, then trace how the declared target frameworks are compared with the lock file. Reproduce the missing NETStandard.Library warning in VS Code and compare it with the successful dotnet restore result; done means the false unresolved-dependency warning no longer appears.