Hello, can you please explain why [(6,0,False)]?

One2many and Many2many fields use a special “commands” format to manipulate the set of records stored in/associated with the field. Read more about this at https://www.odoo.com/documentation/14.0/developer/reference/addons/orm.html#odoo.models.Model.write but note that for v15 and higher, we support a simpler method - discussed at https://www.odoo.com/documentation/15.0/developer/reference/backend/orm.html#odoo.fields.Command

Can you provide an example for how to use this in v16? I don't understand the documents you linked to and I am trying to use this to clear the "Organizer" from Calendar Events.

It is probably easier to manage the Subscriptions based on your unique needs - see https://www.odoo.com/forum/help-1/remove-followers-from-so-except-user-211569