I created a netstandard1.4 library (csproj) which uses System.Net.Http, and the highest available netstandard1.3 listed in NETStandard.Library meta package references System.Net.Http v4.1.0.
I reference this library from a .Net Core console app which targets net461, and the latter has System.Net.Http v4.0.0.0 in GAC. During build I get a warning regarding library versions conflict, and at run time get a FileNoFoundException: "Could not load file or assembly 'System.Net.Http, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies."
Also, in project references (in solution explorer) System.Net.Http v4.0.0 is shown. This looks pretty confusing, since I expect that once I referenced NETStandard.Library and target netstandard, I should not care about such versions consistency, since .NET Platform Standard docs claim that netstandard 1.4 is supported by net461 and higher, and netstandard 1.3 is supported by net46 and higher.

UPDATE: I was also able to reproduce this problem when the library is xproj-based.

Here is the link to the sample project which reproduces the bug