How is TortoiseHG not the standard deployment for Mercurial on Windows? Google "Mercurial Windows". I get the this site which has TortoiseHG as the first download link, labelled as "All-in-one installer", with alternatives labelled as "less friendly". The next results are similar, pointing back to the same page again, TortoiseHG itself, or don't even mention anything else. I've never seen anything else recommended. Am I missing something?

I don't see a workaround that just copies one file. I see a workarond that requires downloading (and executing) multiple modified files from various websites. That's not exactly advisable nowadays.