Hello, if Nokia starts to make its own Native Apps then this will contradict their own claim of Pure and Secure Android for its devices. By Pure and Secure it means that Nokia wants its user to enjoy the Stock Apps and Services provided by the Google themselves and get faster updates. So if they go on making their own Native Apps like you mentioned, the scenario will be like of the Samsung Phones. Basically their phone has two or even three apps for the same function like Gmail-Email, Bixby-Assistant etc. and this is one of the reason Samsung isn't able to provide faster updates to its user even on its flagship devices. And also since Nokia has just made a comeback so they might not want to spend resources on something that is already there and won't have specific value.
If Nokia create their own apps then, as mentioned above, they cannot claim it to be pure, secure and up to date. Not only that but it would mean that the Nokia 3 would no longer be an Android One device.