CoC specify suggest.completionItemKindLabels for Tmux source

[CallumHoward]

CoC has an option suggest.completionItemKindLabels from here that allows labels to be shown next to completion items like this:

As you can see in the screenshot though, it seems the Tmux complete plugin doesn't specify a label. For some reason it doesn't even match the catch-all default label icon that I have set (see first result in the following screenshot which comes from coc-tabnine source):

Happy to provide further clarification if this doesn't make sense