Are bllacklisted webms with sound supposed to play?

I just opened a webm that had music (post #2433506) that at the time was rated q, so was blacklisted when the page opened, but the music began playing regardless. Is this intended behaviour? Makes it a bit harder to find which of the tabs I've just opened is playing music and why.

This occurs for me as well.

I think it's because a personal blacklist only leads to media being hidden through CSS whereas all the content is still loaded and rendered in browser.