I don't disagree
And neither do I I was really just throwing out the quick and dirty alternative.

This is not "strictly" true.
I did try that on a recent project I inherited which has an IFrame in it. I basically wanted to push a button in the iframe page when a button was pushed in the main page. It was a total nightmare and I eventually gave up and went a different route. I figured saying that it was impossible was close enough to be true to be useful.