I have confirmed that there is no setting checked for Hiding any sorts of grades in any course, sub-account, or root-level account. This is happening on current courses within the current term.
I contacted Canvas support, and they told me that they can see the grades while using the parent app. The support tech told me to ensure the parents are using the Parent App on iOS.
However, this morning another parent emailed me saying that they cannot see the grades. I asked the parent to send screenshots of evidence that they are using the Parent App and that they cannot see. This is beyond frustrating.