The player uses quite a few gradient masks to ease the bounds of views. The top and bottom of the transcript scroll view both are gradient masked. Same as the episode title scrolling marquee and the chapter list (if the episode supports it). These are special gradients, too...
Gradients can be interpolated in two ways: by color space (how colors are mixed) or by easing function (how colors change over distance). The default linear easing in tools like Figma and CSS creates a harsh line. The Podcasts app appears to use a custom, easing function: