Salesforce: Attachments roll-up to the related Account

Do you realize that attachments on a Task or Event that is related to an Account, Contact, or Opportunity, will roll-up to appear in the Notes & Attachments related list on the Account record.

See this screenshot:

• First attachment: related to a task in Opportunity linked to Account
• Second attachment: related directly to Account
• Third attachment: related to an email (which is a task) in Contact that linked to Account
• Fourth attachment: related to Contact
• Fifth attachment: related to an email (which is a task) linked to Account

But, they do not appear in in the Notes & Attachments for Contact or Opportunity, is this something weird?

And the worst, this is not customizeable and even to customize the related list for Notes & Attachments.

See this document related to this in Salesforce knowledge.