It's crucial to understand that enabling the “Let others find out” option doesn't expose your identity to strangers or compromise your confidentiality. On the contrary, it facilitates the anonymous exchange of information between devices to improve the journaling experience. Even when other users of the Journal application detect you, your presence remains anonymous and no identifiable details are shared. Apple highlights the security measures implemented to ensure that Diary entries are encrypted when the iPhone is locked and stored in iCloud.
In addition, users still have the autonomy to restrict access to any data point that the Journal application uses as they wish. Your decision to turn off all suggestions will apply to all journaling applications that use journaling suggestions. You control what suggestions are shared with journaling applications that use journaling suggestions by selecting moments that are meaningful to you and adding them to the application. Tips for keeping a journal are designed to protect your information, as they allow you to choose what data to use to make suggestions and what you want to share with journaling applications.
Many of the features of the Journal app are included in the “Tips for keeping a diary” setting, which uses the device's intelligence to generate suggestions for keeping a diary based on your daily life. Regardless of whether the journaling app is hidden, the option That other users can discover is turned on by default and you can continue to turn on suggestions for keeping a diary. As for why the “Let others discover it” option is enabled by default, the Apple spokeswoman explained that this is done so that users can enjoy the benefits of the Journal application “regardless of whether their friends and people around them use the Journal application or not”.