As it turns out, the code does indeed work, and the reason the version number was being stripped out was due to a buried theme option that by default removes all version numbers from all JS and CSS files.
This is in the Jupiter WordPress theme by Artbees, and the theme option is in Theme Options > Speed Optimization > Query Strings from static Files. By default its set to “off” and that removes version numbers. Setting it to “On” appends version numbers as query string parameters. This is a very dumb option to be enabled by default, but now we know.