In the demo
Not exactly, but sort of! We have 8 sample words in the demo, and you almost definitely know those words. But...if you tap those words, you'll find some sentences that may well include some new content for you, and you can jump into learning the advanced words in those sentences.
In the August beta
The beta behaves similarly to the demo, so to access the advanced content, you'll want to use the same strategy above (tapping on words that you probably know, in order to access the advanced sentence content)
In the later beta versions/final release
Yeah. Notice how you can swipe on words to mark them as 'known' or to skip them? You'll do that a fair bit in the beginning, until the app figures out what level of vocab you need and gives you a frequency list that is more in line with your level.