It isn’t. My use case of podcasts is not as source of news or current affairs, but rather as a library (kids stories usually, but I think this is the case of anyone listening to time insensitive content). It’s not often we’re waiting for new episodes; we’re more often rummaging for podcasts, and binge listening to all episodes till we move on to the next one.
In either case, it’d make more sense for AntennaPod to set queued episodes for download than inboxed ones (and if it is set to put new episodes in the queue, it’d download them too).