It holds student-centric, self-paced products. The big publishers will pound their fists swatting away Boundless and miss the real revolution.
Also, good teachers, teaching from good textbooks, to well fed, happy students is not done often. It's not a terrible approach.
As for your second point, I too was a teacher a few years ago. Great teachers can work wonders with a good textbook. For example there is a lot of great evidence/support for the Direct Instruction model which requires extraordinarily well curated material.
But the real question remains, how do we repair our STEM education system in this country (and many other parts of the world) for happier, more capable workers and a more competitive work force?
Student centric learning tools offer amazing potential for scalable and cost effective solutions.
Of course these students who enrolled were mostly self driven knowledge hungry programmers. I have no idea how it generalizes to something like learning long division or historical facts by students who would rather play video games than attend school.
But "student centered education" is definitely a boon to those who crave knowledge and who are not lucky enough to have the best teachers or the best text books to learn from.
What does that even mean? Self-paced isn't a property of the textbook, it's a property of how it's used.