It emphatically is NOT shift-command-hyphen on ANY Mac. It's shift-option-hyphen, and has been since the Reagan Administration.

You're right. It is as you describe on my 2015 MacBook Air running 10.12.6.

But on my 2009 iMac running 10.11.6, using LibreOffice, option-hyphen did produce an en-dash, but command-hyphen did. So either LibreOffice or some configuration setting somewhere on this Mac is responsible for this nonstandard behavior.

Thanks.

Why do you have command and option reversed? Are you using a non-Apple keyboard?

This is curious.

I use an Apple keyboard with a numeric keypad on the right. From left to right on the lowest row, the keys are Control, Option (Alt), Command, Space, and so on.

I was using LibreOffice 5.1.6.2 to try this. It looks like LibreOffice has remapped the keys.