Well, "force" is a bit of a misnomer here. More like they allow apps to categorize their notifications. The result is exactly what you expect: some apps don't categorize notifications at all, and others (including Google ones) do it in a way that's misleading or designed to make the mechanism useless. There is a big conflict of interest here: the notifications users want to shut off the most are exactly the same ones the vendors want displayed the most.
The missing ingredient here is Google punishing bad notification categorization in some way (e.g. by diminished ranking in the Play Store, or failing the review process), but seeing how Google itself doesn't isn't too keen on clear categorization in their own apps, I'm not holding out much hope.
The missing ingredient here is Google punishing bad notification categorization in some way (e.g. by diminished ranking in the Play Store, or failing the review process), but seeing how Google itself doesn't isn't too keen on clear categorization in their own apps, I'm not holding out much hope.