See the below Pipeline script:
{{
build(
job: "pipeline_subjob2",
parameters: [
[$class: 'StringParameterValue', name: 'foo', value: 'bar']
]
)
}}

If 'pipeline_subjob2' has a parameter 'foo', this will work as intended ('foo': 'bar' will be passed). However, if 'pipeline_subjob2' does not have a parameter 'foo', it will not be passed from the pipeline.

This worked previously (in Jenkins 2.0) and I hope the change is not intentional.