update vs. undelete in Apex Triggers

Based on the Implementing Triggers training module, there are only four DML operations for which triggers can be executed: insert, update, delete and undelete. But, when an undelete operation occurs, does that also count as an update operation, whereby the sObject.IsDeleted value is toggled?

To settle the matter for my own benefit, I create an Apex test to validate my assumptions. What I learned and confirmed were the following:

• Only one of Trigger.isUpdate, Trigger.isDelete and Trigger.isUndelete will ever be true during trigger execution. This means that the three operations are indeed distinct and constitute different trigger contexts.
• The ALL ROWS keyword is required to retrieve soft-deleted records that are in the Recycle Bin

Below are the trigger and its test class I used.

AccountTrigger.cls

AccountTriggerTest.cls