The nomagic doc page you linked does not describe it clearly and is confusing. It also does not say what "Action Language" mode you need to be in for it to work (or if it matters). Using your screenshot in this post it made more sense and leaving it on "English" action language also worked.
As others have mentioned, if the reference name has spaces, it doesn't seem to work at all. I also had to use "this.*" (where * is a pin name) when I was not using a specific value property if that makes sense?
I have two questions:
1. Is there a language/naming rule page? Something that says not to use certain special characters, don't use spaces, use quotes, double quotes, any special reserved words, use this.*, etc?
2. Is there a way to evaluate/test guard syntax? The evaluate box doesn't seem to actually reference values or work when using this.* references.