I just did a test where I created a new JPG from a BMP file, such that it had no metadata to start with, then set the Date Taken field using Opus. I set the date to something distinct to the filesystem created and modified timestamps, to make sure I wasn't just seeing those in other software.
The date I entered was visible in both File Explorer and Photoshop.
So if you think there is a problem and you want us to fix it, you'll need to provide more information on the exact steps, or example files where the problem is seen, because the problem isn't happening for us and probably isn't as simple as you assume it is.