I wouldn't say it's random - more like FE was the random one as almost all their other CE's used CDs, and in other regions FE used a CD too. I'm happier with my FLAC rips than the MP3 encodes from the stick too 😅
I meant Nintendo Europe is being random by switching between usb and cd per release title. You would think they would choose one and stick to it on all games going forward.