It's hard to say if, for the average user, it's easier/more likely that they will get to the Netflix app (whether on official store or not) by clicking a link from the Netflix website than by doing a search for it in the Play Store. If they see a Netflix ad with netflix.com address on it I imagine they'll just type that in their mobile browser. A page would open, which detects the platform and prompts them to click "here" to install app. And now that link can be outside of the Play Store, the user doesn't even visit it.

But for all those that might mistakenly look for it in the Play Store, you can have a stub app there that just redirects them (opens a browser page) to where to get the real, outside the store app,

They claim they made it easier to use alternate stores in this very release, and the inability of an average user to google is overstated.

There's no limit to interest to Netflix, Stranger Things won't watch itself.

Inability != Willingness and motivation and enough attention span. Anyone who has ever worked on a conversion funnel would know.

The next release will take 4 years to reach 80% of users based on past experience. Only half of users are even on 9 which released last year.