Just some thoughts ....
There are developers who make great apps. We all love those and are willing to pay "more than those $ 0.99".
But, on the other hand, there are also some "developers" who don't even bother to create any usable app. They link in their "apps" to foreign websites and are happy to get $ 0.99 for this crap, not even bothering to update if the website changes.
Now, with those full screen ad videos, I would not be surprised if the number of crappy apps will increase - after all, those people never intended to make money from happy customers. Of course, everybody will delete those "apps" after opening them for the first time.
But there is a never ending stream of new users and some developers might be happy throwing garbage into the app store - a new app every week - and get some revenue from ads per app for a short time.
Everybody happy except the users and, in the long run, developers who create valuable apps?
And, btw, if I download a free version of an app to help me decide if it is worth buying the full version and this app contains a full screen ad video, I won't wait and test the app. I will delete it immediately and never think about buying the full app. We live in fast times, nobody pays attention for 5 or more seconds on something that seems to be just annoying.