It looks like the inline Apple Podcasts player is causing that, though it's not clear why since it's loading unencrypted MP3s directly from the authors S3 bucke

It looks like the inline Apple Podcasts player is causing that, though it's not clear why since it's loading unencrypted MP3s directly from the authors S3 bucket. I guess their player eagerly sets up DRM playback at startup rather than waiting until it's needed, or they're using EME for something else (fingerprinting?).