Can't be language families—they've got Spanish, Italian, and Portuguese, so French would be an obvious choice to include.
The inclusion of Estonian is particularly odd. It's a very small language (1.1m native) and is the only non-Indo-European language in production or development.
Reminds me of the language learning app Lingvist, which for a while had only German, French, and Estonian for a similar reason: the company is Estonian.
The inclusion of Estonian is particularly odd. It's a very small language (1.1m native) and is the only non-Indo-European language in production or development.