When is extend-glob required in a [type section?

[paddyroddy]

I noticed that in the docs there is this example, but is the extend-glob required here? I tested a similar case where I omitted and it seemed to work.

[type.po]
extend-glob = ["*.po"]
check-file = false

I'm assuming this is useful if you have a file x.po1 that you'd like to treat like x.po.

[epage]

Extend glob is needed when

• the type is previously undefined
• you want to capture more cases

[paddyroddy]

* the type is previously undefined

In my case, I was dealing with .tex files. What does undefined mean here?

[epage]

Undefined means its not reported in typos --type-list