Can a content specialist with expertise in Integral Calculus please look carefully at the sequencing of the course material in this subject? I'm not too far into it, but I am already seeing quite a few articles, practice exercises and videos that presuppose knowledge that is actually encountered later or perhaps not at all. The Advanced Placement (hereinafter referred to as "AP") Calculus AB (and I believe also BC) do contain some of this missing content and corrected sequencing. Here is what I have found so far. Although I am typing this in the web version's support community, I prefer to do all of my education in the iPad app version, so I don't have the Ask A Question option that was recommended to me to report this issue.
1. In the first topic, Definite integrals introduction, the first playlist, Definite integral as area, starts off with an article, Warmup: Definite integrals intro, followed by a practice, Definite integrals intro. Both of these presuppose knowledge of what an integral sign means. Even the article is just made up of problems, no introductory material. The first playlist, Definite integrals intro[duction], in the topic Accumulation and Riemann sums in AP Calculus AB starts out with two videos, Introduction to integral calculus and Definite integrals intro[duction], that I suspect belong in the leadoff spot in Integral Calculus, although I haven't viewed them yet.
2. In the same first topic, Definite integrals introduction, in Integral Calculus, the second playlist, Definite integral properties, starts off with a video, Integrating scaled version of function. Good, a video! But in this video, Sal refers to some video on Riemann sums that hasn't been encountered yet.
3. I skipped the rest of the first topic in Integral Calculus and went onto the second, Riemann sums. In the first playlist in the topic, also called Riemann sums, the 3rd item is an article, Riemann sums worksheet. While this article introduces students to the three types of Riemann sums (left, midpoint, and right), before it ever talks about what these types are and how to distinguish between them, it starts out with "review" problems asking students to identify which type is shown in accompanying graphs. After these "review" problems, there are brief segments that show each type of Riemann sum in a graph without pointing out how to identify or use them. There is then another "review" problem for each graph that asks students to use this type of Riemann sum to find the area of the given rectangles. This article is then followed by a practice exercise, Left & right Riemann sums, which contains similar problems on the not-yet-fully-explained left and right Riemann sums.
In the second playlist, Left & right Riemann sums, in the Accumulation and Riemann sums topic in AP Calculus AB, there is additional material preceding the Left & right Riemann sums practice exercise, including a far-more detailed and informative article, Left & right Riemann sums, that serves as a better introduction than the one included in the Integral Calculus course and should be duplicated in that course, somewhere early in the Riemann sums playlist.
This is as far as I've gotten in my Integral Calculus studies. If I come across any other issues like these, I will post them here.