I spent years as a foreign language teacher, curriculum designer and eventually language school owner. That experience has largely made me numb to these sorts of products and claims.

Learning words isn't the same thing as learning a language. Spaced repetition is exciting to people when they first learn about it, and it's great for memorizing certain types of discrete information (e.g. the capital cities of each country, the periodic table of elements, etc...) Memorizing a dictionary doesn't lead to language skill, though. At best it's a useful stockpile that will speed up your later learning efforts, but at the cost of thousands of wasted hours.

If you're determined to learn a foreign language from a heavily memorization based method, at least use an audio-lingual system that will give you decent pronunciation! The Pimsleur Approach will do that. It will beat not only words, but pronunciation and grammar into your head. It's mind-numbingly boring especially after the first one or two languages, but less so than a vocabulary memorization app.