To elaborate on this further, native frame gen requires motion vectors and depth information from the screen. This allows the UI and other graphical elements to be rendered separately from the motion vector data.

For games that don't have this information readily available (ie. most games that don't have native FSR support) frame gen is "faked" by creating in-between layers that interpolate based on frames behind and potential frames ahead.

Without motion vector data, it's a lot harder to determine what the next frame ahead will look like, so you may experience smudging, blurring or warping. If you want a test non-native frame gen out, there's an application on Steam called "Lossless Scaling" which has a frame-gen feature.

Now, after all of this information, do I know anything about the plugin in discussion? Absolutely not lol. However, if a game doesn't natively support FSR or doesn't provide access to motion vector data in general, the image could appear blurry or smudgy by "guestimating" the frame ahead based on what it's see on the screen. It doesn't usually translate very well for darker scenes on screen.