When a string is displayed in the BlueOcean UI from an "echo" step, the string "Print Message" is displayed IF the string being echoed contains a substring that matches the contents of any environment variable. 

Repro steps:

Create a pipeline with this code:

pipeline {
    agent any
    stages {
        stage('test') {
            environment {
                THING = 'foobarbuzz'
            }
            steps {
                echo "blah"
                echo "foobarbuzz"
                echo "foobarZZZbuzz"
                echo "This is a $THING here"
            }
        }
    }
}

Run the pipeline via Blue Ocean

Observe that there are four step labels displayed in the Blue Ocean UI. (see attached screenshot)  The first and third steps display the strings from "echo" as expected.  But, the second and fourth steps display only "Print Message" and don't show the expected string.  The user needs to click the step to expand it to see the string.  I would expect that all strings from all echo statements should show up in the main Blue Ocean UI and would not require some to be manually expended.