Thanks for tagging me!
Well, we originally had it so that a new reader would land on the first episode uploaded, and then would have to read through the series which favorited long form (which the site was built to cater to).
But because of the heavy influx of short form series, there was a greater demand from the creator community side to shift this first reader experience to exposing them to the most recently updated episode. This became the standard early last year.
As to why we have to cater to one form over the other - part of it was trying to standardize the reader experience and trying to get some consistency to the site. We do understand how this is not ideal for every series, and we will be working on this at a future date. I really do want to implement the "read first episode" button again and have more customizability on the creator's end.
The dashboard organizing tool is just to help you organize the overview for your episodes and not to reorder the episodes in the series list itself.
That's a cache problem that we have to address. The current placeholder system is fairly simple, it just bookmarks the most recent episode you left off on and doesn't take into account if you've already read the episodes or are just visiting to look at the comments. This will be addressed in a future build.