Cloud save
I tought the map is generated at the creation. It have borders, since i can set the parameters. File size isnt "huge"
Thats why its weird (to me) to not have a cloud save. Compared to something else, it could be a thing easily, since its not and endless map.
Since its alpha, i understand that they dont want to spend dev time to this.
I rather think they aware of some bugs and causing some players save corrupted. Just by logic. but your "file would be too huge" idea is still can be true somehow.