Exactly right. Unless everything is exactly right (such as the operating system, drivers, browser, video card, monitors, cables, etc.), the chances of getting the actual 4k on a PC are near zilch.
As for dung quality, you know the reason as well as I do - at least one piece of your streaming playback isn't quite right.
As Louis said correctly, he doesn't pay Netflix for a 4k package to make it hard for him, but the opposite should be true - paying for top-tier service should provide top-tier convenience because, at the end of the day, this is what Netflix is - convenience for the price of subscription.
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Learn to use Netflix on Windows. Includes setup for browsers and the app, plus requirements for Ultra HD and HDR on Microsoft Edge and Windows 10 or later.
help.netflix.com