That is right. Microsoft usually is pretty quick, but every app store is different and up to each one. Microsoft says below it's usually a few hours. Google is quick but Apple can take 1 to 14 days. Lately Apple has been pretty quick as well, usually 1-2 days.
There are two version of outlook and where you add add-ins is different
Desktop client that you install on your PC:
File (top left); Manage Add-ins (bottom page middle); Search for Add-ins
Web client you access to a browser (Chrome, Edge, Safari, etc.)
Create a New Message; Click the 3 dots bottom middle of the email window; Select Get Add-ins; Search for Add-ins
Whether you are using the desktop client or browser it should take < 30 seconds to Find.
"When you finish creating your app's submission and click Submit to the Store, the submission enters the certification step. This process usually is completed within a few hours
, though in some cases it may take up to three business days. After your submission passes certification, it can take up to 24 hours for customers to see the app’s listing for a new submission, or for an updated submission with changes to packages. If your update only changes Store listing details, the publishing process will be completed in less than an hour. You'll be notified when your submission is published, and the app's status in the dashboard will be In the Store"