Hi Jonghyun, thanks for sharing this concern.
This is the intended behavior for calendar views: all fields are shown in expanded records. At this time, we don’t offer a way to specify which fields are shown or hidden in expanded records of calendar views, or in shares of calendar views. This is a frequently requested feature and we plan on supporting it within the next few months, so that calendar view shares can be customized like other shares.
Note that shared calendar views do respect the calendar view’s filters; in other words, only records that are visible in the calendar view are visible in the shared calendar view. The above limitation only concerns fields, not records.
If you’d like to create a shared calendar view but need specific fields to be hidden, you can create a shared grid view instead (which supports hiding fields), or if the share does not need to stay up-to-date, you can duplicate your base, delete any fields from the duplicate that you’d like to hide, and share a calendar from the duplicated base.