The wperry link will mark the podcast as listened to, which is the same issue as your workaround that you find unacceptable.
I do think, however, that you can workaround this issue by right-clicking and choosing refresh.
And the i Tunes COM object does not seem to expose a way to update individual podcasts, only the entire list.
This is most annoying as some have dropped off the RSS feeds so I have to manually find them...
(trying to see at the moment if I can put them inside the right podcast section and not just as a mp3).
The reason for the emphasis is that i Tunes doesn’t actually list this one in their specifications.
However, they have repeatedly iterated to members of the Libsyn team the size limitation, and have requested larger images be fixed prior to any additional work done on their end to kickstart a show into updating again.
I have the options for each podcast set to that, and this has never happened.