The subject (title) is replaced by organizer's name and the attendees of the ongoing meeting are hidden when the event is marked as a private or confidential.

When creating events in Google Calendar, users can set different levels of privacy for each event. The options for visibility are as follows:

The "Private" option is available when creating new event in Microsoft Outlook. When an event is marked as "Private", the subject (title) is replaced by organizer's name and the attendees of the ongoing meeting are hidden.