From what I understood, while HS2 has better graphics, the options to customize, which may be one of the reasons the updates of Eternum take longer than Once in a Lifetime did. But we never know, after all he always wants to surprise with new stuff, as well the updates always have a lot of content, he's like that, likes to show his magic.
Last days he didn't comment much around here, as he likes to fullfil deadlines for releases, but maybe he grabs some time in the future and explains a bit better if he can.