I don't know the answer to your question, though I suspect it's that Jellyfin doesn't support menus.

What I've always done is rip each track to a video file. Jellyfin's movie metadata DOES support extras: https://jellyfin.org/docs/general/server/media/movies/ and video formats like mkv support additional audio and subtitle tracks. With multi-track video format and extras support in the Jellyfin native menus... it's possible to rip the vast majority of DVD content into Jellyfin. But ISO is not the preferred format to do it.

The main thing you'd lose here would be interactive menu features or choose-your-own adventure video codes into menus. Those DVD titles are pretty rare though.

VLC might have DVD menu support for ISOs, fwiw. I have a vague recollection it might, but I'm not at all sure.