Voice Control > Shortcut > Run Javascript on Webpage doesn't work

I set up a custom command in Accessibility > Voice Control to trigger a Shortcut that is supposed to run Javascript on a Safari webpage.

Everything seems to work, except the JS doesn't affect the webpage:

The voice command is detected, the shortcut executes without error, a Shortcuts confirmation banner displays. I also added the shortcut to the share sheet and executed it manually. Same result.

JS is enabled in Safari settings

Allow Running Script is enabled in Shortcuts setting

The same shortcut/javascript works fine on a Mac, so I know the shortcut/javascript works. Just not on the phone.