Referenced assemblies not being packaged in VSIX (or not being installed)

[csuzw]

I'm trying to create my own connected service. I have been using the SinglePage sample app as a guide. I have some logic in my view model that is failing with the following error:

=== Pre-bind state information ===
LOG: DisplayName = Newtonsoft.Json, Version=11.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed
 (Fully-specified)
LOG: Appbase = file:///C:/Program Files (x86)/Microsoft Visual Studio/2017/Enterprise/Common7/IDE/
LOG: Initial PrivatePath = NULL
Calling assembly : Flurl.Http, Version=2.4.0.0, Culture=neutral, PublicKeyToken=null.
===
LOG: This bind starts in LoadFrom load context.
WRN: Native image will not be probed in LoadFrom context. Native image will only be probed in default load context, like with Assembly.Load().
LOG: Using application configuration file: C:\Users\rjc\AppData\Local\Microsoft\VisualStudio\15.0_fa79a415Exp\devenv.exe.config
LOG: Using host configuration file: 
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: The same bind was seen before, and was failed with hr = 0x80070002.

Newtonsoft.Json is referenced though:

When I look in the directory that the extension is installed into it has hardly any assemblies:

I don't know why Flurl.Http and Microsoft.IdentityModel.Clients.ActiveDirectory assemblies have been copied but other assemblies like Microsoft.CodeAnalysis.CSharp and Newtonsoft.Json that should also be there are not. Am I doing something wrong or is this a bug?