In-app update API returns UPDATE_NOT_AVAILABLE status

Question

I uploaded two bundles to Google Play Console - 19 and 20 code version. I opened the internal sharing app link of 19 code version of the app and installed it:

But when I launch the app In-app update API returns UPDATE_NOT_AVAILABLE (== 1) status:

Update is available 100%:

Answer 1

It seems I can't just use App bundle explorer

Though it also has Internal app sharing link:

This one is not going to work though it's also called internal app sharing link...

We have to use this web page to upload apps to test In-app update API https://play.google.com/console/u/2/internal-app-sharing

Google just made it really bad. Everything is called the same, you can find internal app sharing links from different places but they are not the same