HTDP teaches how to program. Philosophy does not. That's pretty much the entire difference, they're in different categories of books. Philosophy assumes you know how to program, and attempts to teach a way of programming. HTDP starts from the beginning with no assumptions about the reader's ability to program.
https://www.goodreads.com/en/book/show/39996759-a-philosophy...
https://www.hackerneue.com/item?id=37975558
Looking over the ToC there seems to be at least some overlap, but at a more basic level and sans the over arching concepts of APoSD.