I'm loading a declarative pipeline from a file, I substitute variables in it from a Jenkinsfile and then run the declarative pipeline. 

When I do this, I'm able to put if statements around stages and within stages without having to use the script block. I'm able to hide stages too with this method if I wrap the stage in an if-block. This all seems to work well but I'm concerned this isn't appropriate bsaed on what I've read. 

Any idea why this works ?

I've attached an example file that I load and run.