How Does tanka work?

how does tanka work? I followed the example Using Jsonnet | Tanka.
I have a question.
with this example, when i use jsonnet command to gernerate yaml:
jsonnet -m manifests main.jsonnet | xargs -I{} sh -c “cat {} | gojsontoyaml > {}.yaml; rm -f {}” – {}
the result like this : it has deployment and service fields.
but if i use tk command to show yaml , it has no extra fields like above:

I am so confusing about this.