It’s a misunderstanding of the meaning for “most rigorous” category. It doesn’t mean “… conceivable” but “… reasonable”.
(Obviously if your school does Precalculus=>AB=>BC and you took precalculus as a sophomore, AB as a junior, you’re expected to take BC senior year if you’re aing for a STEM major. But if you’re taking precalculus junior year, as most future STEM majors are, you are not docked for taking the next course in the sequence! And adcoms do not have time to ponder the way each high school works, unless it’s a feeder and they have had longterm reservations about something…)
Anyway adcoms have their own criteria, in part because some competitive HS have completely lost their senses, such as the one that only gives “most rigorous” to students with 16 APs or the one here only ~5 students per class get the designation.