That is not what the ICE doc says. If school opens 100%, students have to go. If not, students can take more online classes than usual.
The announcement is available here as a PDF from ICE website: https://www.ice.gov/doclib/sevis/pdf/bcm2007-01.pdf
This has put an immense pressure on universities and international students. In particular, due to the very short time to make any changes, this announcement has posed a serious challenge.