The HidePatronName syspref says: "(Show / Don't show) the names of patrons that have items checked out or on hold on detail pages or the "Place Hold" screen." This syspref is also hiding the patron name from the checkin screen. If that is the intended behavior, we should clarify this wording. If that's not the intended behavior, we should change the behavior.
I've confirmed this is a change between 19.11 and 20.05.
Looks like this is caused by a line added in bug 23433. I'm not clear whether or not it was intentional.
The first occurrence of hide_patron_infos_if_needed=1 is coming from commit 258c538e76914e6c2023242b555bb38c6f1970b9 Bug 22203: Holds modal does not link to patorn account And I've asked Nick, see bug 22203 comment 9.