A family of Microsoft word processing software products for creating web, email, and print documents.
Thanks for the clarification. Since you have verified that the install method makes a difference, you should definitely report this to Microsoft using the Feedback facility.
There is a thread in the TechCommunity forum which demonstrates how you can change certain registry entries to enable the new Office look. It mentions Word 2021, but it would be worth testing even for Word 2019, I suppose. See https://learn.microsoft.com/en-us/answers/questions/713613/not-getting-the-new-visual-refresh-in-office-2021.