When you share your screen or an application, you can improve the quality based on the type of content that you're sharing. By default, sharing is optimized for text and images, providing high resolution for content like documents and slides. However, you can optimize to ensure a higher frame rate when you share things like video, animations, or dynamic applications.
https://help.webex.com/en-us/ntx2aid/Share-Motion-and-Video-Content-in-Webex-Meetings-and-Webex-Events-Slow-Channel