Hi Fam,
when a user wants to confirm a Quotation with approval rule, he can see the activity "Grant Approval" the chatter. What stops the user from approving it himself? It could be in the chatter as a notification but not accessible to the user. It just undermines the whole purpose of approval rights.
Thanks
Did you try having the User who is requesting Approval complete the Approval Activity? You will see that the Quotation remains unapproved, and they have to request Approval again.