If I built a Mac app, the reason would be that I use a Mac, as do a lot of other people, and native apps are a lot more pleasant than non-native apps. I don't really understand why it's "restrictive"? There is no restriction happening.

The author had to decide between making something excellent for some people or mediocre for everyone, and chose the former

You may use Pepakura if you’re running windows. Not sure if a web or linux alternative exist.

The same could be said about pretty much _any_ software.