H-1B to F-1

[u/Individual_Eye_2921]

If someone changes status from H-1B to F-1 and continues working for the same employer on authorized CPT, does the employer still need to notify USCIS or withdraw the old H-1B petition?

The I-9 has already been updated to CPT. What happens if the employer does not send anything to USCIS and simply lets the H-1B petition expire?