NWC has always approved sci-fi in HoMM sub-series and said it belongs there because Heroes is part of MM universe.
http://www.heroesofmightandmagic.com/fo ... =interviewQ: DOES SCIENCE FICTION BELONG IN HEROES?
And this was written after the Forge town was cancelled, so one can tell that NWC did it under pressure (i.e. death threats) and was still considering sci-fi authentic to HoMM.
Q: WILL THE FORGE RETURN?
GF: Perhaps, but not in its current form.