Gmail’s Email filter checkbox or radio?

I was just trying to filter the emails I was getting from the particular site and the time when I clicked on filter messages like these and then to Create a filter to this search, it opened some options which confused me being simple .

See this

Now every option has checkbox which means a user can select multiple options.

My concern is with last two options gmail is providingsee this

So what is this?

  • Is it something google did intentionally?
  • Is there anything hidden about these checkboxes?
  • Although I can't select never when always is ticked but to check never, I have to uncheck always first and then choose. So why not a different div with radio buttons in these two?
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