Headless _index.md doesn't hide it from .Page

.
└── content
    ├── _index.md
    └── pages
        ├── _index.md
        └── about.md

Having list.html as

{{define "main"}}
<ul>
	{{range .Pages}}
	<li>{{.Date.Format "2006-01-02"}} | <a href="{{.RelPermalink}}">{{.Title}}</a></li>
	{{end}}
</ul>
{{end}}

For some reason, main homepage is rendering Pages section. But accessing Pages, shows:

* 0001-01-01 |
* 0001-01-01 | About

Why is there empty title here?

Edit: I suppose it’s caused by _index.md not having a title tag. I tried headless: true but that doesn’t solve it.

I think you misunderstand headless. Not having a title is NOT headless.

For your case, probably, the build options per frontmatter should do the trick.

A second option for a whole bundle/leaf to be headless would be setting headless: true in your index file