They already went to a cutting edge private school that has a 100% graduation rate. I could see what you mean if it was just one student, but these kids were working independently. The school is the common thread.
What you say might be true if it were an easy accomplishment for an adult. Like those kids who are 10 years old with 2 businesses. Then you find out that their parents have 5 businesses. What are the chances that two students independently have outstanding mathematicians as parents?
Not only that, but they also explained their proofs. Watch the video. It’s not a “kid with a boring online business” story.