Text instead of word count

I turned on "show word count" in the "General preferences" pane. However, in the bottom of the editor window, I only see text: WORDS_PLURAL_ STRING etc. (cf screenshot)

I'm using my own theme for previewing, if that is relevant.

No files, tests, or entry points are named. Reproduce the issue by enabling “show word count” in the “General preferences” pane, then trace the displayed WORDS_PLURAL_STRING text and the localization resources it uses. Done means the editor’s bottom bar shows the word count instead of untranslated string keys.

Written by the indexing model from the issue text.