Given the holistic and unpredictable (from the student’s point of view) nature of many of the highly-competitive-for-admission schools that they are applying to, a school saying that “we expect you to maintain your academic performance through senior year” (without any specific thresholds) will probably cause a lot of worrying by a student getting his/her first B or two in senior year. After all, even if the risk of rescission is low, the stakes are high – if rescinded in the summer, the student has few options other than open admission community colleges and perhaps the least selective four year schools that are under capacity even up to the first day of classes.
I figure an A student can get a couple of B’s and B student can get a couple of C’s. If you want to drop a course, you must call the college and find out if they care. But really, my kids didn’t find the pace of senior year that bad - and the second half of it you are no longer trying to juggle applications. My younger son slacked off a bit in some of his AP courses when he realized that he wasn’t going to get credit for more than 5 and he already had the fives. He didn’t do disastrously on the APs, but the lack of extra studying did show in his scores. (mostly 4’s instead of all 5’s).