“I accidentally did something that I had to explicitly go out of my way to do, and doing literally nothing could have prevented it”

Multiselect lists are outdated design, requiring prior knowledge of what they are and the use of keyboard (that you might not have if using a touchscreen device) for a simple interaction with a webpage is terrible UX. The issue is that it’s how browsers render them by default, a ‘proper’ multiselect requires a bunch of css and javascript.