I personally know several kids who overextended themselves in APs (some of which they had ZERO real interest in) because they were in the AP rat race- and they had plenty of HONORS level courses available. The result was some Bs in some APs. The Bs bring down the GPA and the additional APs ended up hurting them in elite college admissions. If you read CC enough - first question is always GPA, second test scores. That said, 1 B won’t be the deciding factor on keeping kids out of elite schools.
There are many ways a student can challenge themselves with most rigorous without loading up on extraneous APs.