no value substitution when key is used as template

[haayman-imagem]

I'm using the English string as the key of the translations, e.g. for Dutch:

{
"Continue": "Verder",
"Found {numResults}": "{numResults} gevonden"
}

When switching to English on our site, the translations object is almost empty, we just display the original key.
But it turns out that the {numResults} isn't substituted. We see the entire 'Found {numResults}'
So, is this a bug? Or is using the key as the template string not supported?