@Scit @fredo6 I see the same issue - all MP4 videos seem to be encoded as 25FPS regardless of what is set in the Animator clip creation UI. I am using a Mac Studio with macOS 26.6.2. I am not sure what version of ffmpeg I have; I think it was "inherited" from my previous Mac when I installed this Mac Studio and migrated the contents from my prior Mac.
Edited to add: I just updated ffmpeg to a build from a few days ago (downloaded from https://ffmpeg.martin-riedl.de/) and there is no difference. MP4 clips are still encoded as 25FPS even when, for example, 30FPS is selected in the Animator GUI.
This is causing some grief in my video editor (iMovie), complicating how I time some voice-over with the video content, and also with how I have the editor dissolve from one clip to another when frame-by-frame synchronization is important.