That may have been true a couple years ago, but they are rapidly expanding. They now include calculus and diff eq with plans to go beyond. They're even researching med school related content for the future.
That being said, I wouldn't take that as a reason to not pursue this.
Looking at what's on there, I'm really not convinced. You could not get through an physics, engineering or math program on the material that is there, not even close. If I search for, say, complex analysis, all of the material I get is about complex arithmetic. No multivalued functions, branch cuts, p.v. integrals, harmonic functions, DEs, nothing. It's all what they expect you to know going INTO the course, or that they cover in the first two days.
Similarly, if I go into the physics topics, they are all <= intro courses, at best. Optics? Doesn't talk about fourier optics, lasers, etc. E&M? Doesn't seem to mention Maxwell's Equations anywhere... enough said. Quantum mech? Nothing. Statistical mech? Nothing.
Okay, how about math? Take a look at the differential equations stuff. No higher order, no series methods, no numerical methods, no coupled systems, no non-linear. Probability? No markov chains, MCMC methods, or anything except basic RVs and statistics (which is not the same thing as probability). Same for linear algebra: no fitting methods, no matrix decomposition, no graph theory.
I could go on. The point is that they cover the most basic elements of each subject, and they miss a hell of a lot of important subjects. That's okay, but don't claim that they're anywhere close to being able to educate you at a university level.
That being said, I wouldn't take that as a reason to not pursue this.