Inconsistent "Remove Background" Quality on Adobe Express Website

I have discovered an unexpected relationship between the source videos properties and the quality of the Remove Background feature on the Adobe Express website.

https://new.express.adobe.com/

This finding highlights a significant performance discrepancy I observed while testing high-resolution vertical MP4 videos (2160 x 3840).
When testing, I found two main conditions:
1. SUCCESS: A source video running at 60.00 fps (with a high Total Bitrate of ~95,775 kbps) produced a Pixel-Perfect, clean mask after processing.
2. FAILURE: A source video running at 29.97 frames/second (with a lower Total Bitrate of ~78,883 kbps) produced an Extremely Sloppy and unusable mask.
Key Finding: The only input factor that allowed the AI to perform cleanly was using the 60 fps video source. When the successful 60 fps file was processed by the Express web app, it retained 60 fps but had its bitrate reduced (~65,809 kbps total bitrate). This strongly suggests that the success of the AI background removal feature is critically tied to the source having a higher Frame Rate (60 fps).
Feedback for Adobe Express Team: The current behavior is non-intuitive. Users expect core features like background removal to work reliably on standard 30 fps footage. Please investigate why the AI performance is drastically better—or only succeeds—with 60 fps video compared to 30 fps footage on the web platform. This technical dependency should be resolved or clearly documented for users.