What if a malicious app decides to place child pornography or a crypto mining whatever onto your device - but since its space is "private", can unethical people now legally do that, and simply blame that Google wouldn't let them see into the space, hence they "did not know that it was there"? This would seem to open the door to so very many problematic issues...
On the other hand this seems related solely to "external" storage - I haven't used external storage on an Android for... actually I've never used it iirc. For this Netflix case, would they disallow downloading onto your device unless you have an external SIM? Also, if you used external storage, then how da fuq could they control you popping that external storage into some other device entirely, like a rooted device with a custom ROM!? It would have made so much more sense for internal storage... or possibly I am missing something there.
In any case, that sucks that Google seems more and more to be buying into the "walled garden" philosophy - you know, "for your convenience", aka selling YOU as the product to the investor class.:-(
A quick search seems to suggest there is no known way around this, except to use an older Android OS:-(. I would hope that this would absolutely wake people up to realize why Google cannot be trusted - as if what happened to searching wasn't enough on its own.