Your published date field is a date type, this include hours, min, seconds… So if they are not created exactly at the same time, unique element will consider them all different date. And this is correct.

I think the best option you have is to use :group by after the Search for shows

Another option is to use :formatted as after the published date and before:unique element. At this moment, you will format the date as text (so the RG type will be text and not date).