It's a little inconvenient for someone setting up a new phone to have to wait a full day to install unregistered apps. But while I can't speak for others, it's a price I'm personally willing to pay to make the types of scams they mention much less effective. The perfect is the enemy of the good.
On what basis do you believe that it will meaningfully reduce the dollars lost or persons harmed by fraud, as opposed to simple shuffling around the exact means used?
Give me a break bro. Google are among the biggest crooks in the game and knowingly allow all kinds of fraudsters to use their ad platform. This is all about ensuring their cut.
How would you feel about needing to wait 24 hours to visit an "unapproved" website on your phone? You would pay Google/Apple $25 to get whitelisted so people can browse to your personal website without getting a scary security message.
This is the same thing since it applies to all apps, not just apps that need special permissions.