We stripped every feature that made our product different and put them in an 'app store'. This was a huge change (a lot of work and a big risk), and not something I've seen others do as an on-boarding strategy. Thus, novel. I believe this approach could be repeated by others. It's a far cry from the usual walkthroughs, carousels and prompts.

So basically putting advanced features into a separate section, making them togglable and calling this section an App Store?

They are still mentioned on the homepage and in a form of a carousel at that.

I appreciate that this must've been a significant rework, with all edge cases considered, but sectioning off parts of a software and making them discoverable in a course of normal use is not exactly novel... I mean that's just too bold of claim to be thrown around lightly. The story is still interesting, but something a bit more exact like "Here's what worked for us remarkably well" would've been more suitable.

You can innovate on a known concept by using it in a novel way. I believe that's what's happening here, and I find the idea intruiging, smart and novel indeed.

I think an added benefit is that it makes it trivial to see what are indeed the benefits of the tool : it's what you expect from an email client plus those things, nicely presented together. Just by reading the article and seeing the screenshot, I could evaluate if I was interested in this tool, which is a very rare thing.

Nice out-of-box thinking, I think. But I wonder, ...

If there's nothing novel in the initial version why would people think they would want to switch? What would be the reason?

Could it be that your product without any unique features is cheaper than competition, and adding features costs something?