Regarding students who fail and have to retake courses, note that at least some of the Texas policies count attempted credits, even if the student fails or withdraws from the course after the census date (effectively “wasting” the space in the course).
It is, however, not very friendly to count credits from before high school graduation (AP, IB, college courses taken while in high school) toward such limits, since high school students usually are not specifically following the course plans for a major and other college degree requirements, so many of the transferred credits earned before high school graduation may end up being generic elective credits.