Hi @LisaMM11! These are two very different features
The show up as “away” is essentially an indication that you are on vacation, it indicates to other users that you might not be able to respond or complete a task until you’re back; and no worries, with this option, you will still be able to access your tasks when you come back from your holidays. Only users can enable this function from their account, you cannot do it on their behalf. You can learn more about this feature in this handy article: https://asana.com/guide/help/fundamentals/settings#gl-away.
On the other end, when deprovisioning a user (https://asana.com/guide/help/organizations/basics#gl-free-depro), you are effectively removing them you Organization and they won’t be able to access their task anymore!
Hope this helps to clear things up; but if you have any questions, let me know!