It does actually do this. Do you want the demo document's to zoom? If the document wont fit in the viewport on load, it will zoom. Also, if the document is really small, it will zoom in to fit on load.
BTW I'm incredibly impressed, been looking for something that my girlfriend could use as she's just moving into web design. Muse was pretty disapointing(to say the least). I can see this being a much practical solution. Having seen how good it is I can see myself using it as my go to tool for at least prototype designs.
That's great to hear. If you have any questions/concerns, etc. as you get deeper into it, shoot me an email: ben@easel.io. I'm here to help.