C#: When set to STJ, DecodeArrayConverter code seems to use Newtonsoft members?

[ChairmanMawh]

Some JSON i pasted recently generated this:

Screenshot from browser

I'm using STJ but JsonToken belongs to NewtonSoft. I believe the equivalent is JsonTokenType in STJ

Also, the highlighted variable serializer doesn't appear to be defined anywhere, so I get compile errors with this code section:

Screenshot from VS