Here is a topic from 2016 talking about this.
Long story short, the plain text is only a portion of what is being copied to the clipboard. It also copies, in the case of properties, RSCI formatted data.
What you’re looking for can be done, but it unfortunately isn’t as simple as it seems.
You can get an idea of what it’s putting on the clipboard using a clipboard viewer:
That’s just a public integer property named myInteger