As people have already said, the content is just to help you memorize the parts of the kanji better. They kinda have to keep it easy from the start so that people don’t rage quit too easily from the start. I actually ran into a similar situation when I was having a conversation with a student and tried using 一文字, but they also didn’t know what I was talking about. Honestly, it would be helpful if there was some kind of social note on the word’s frequency so you know it’s something you’re more likely to run into the word in reading rather than speech or don’t run into faux pas like with 男優.
Another thing to keep in mind though is that they are a business too. They have to gate you at least a little bit with the content to keep subscribers longer and make the selling point that they are teaching you X number of words through all their cards.