That Fusion 360 doesn't work on Linux is probably a business decision too, because it packs a lot of web tech. F360 isn't very far from a packaged web app.
Fusion 360 is very much a native app. Qt and all that jazz. Just one that's been nerfed in the name of cloud. Certainly it's trending more towards "cloud based" features over the years. As for Linux support, Fusion was kept around despite never turning a profit because it was the CEO's pet project. To that end I'd expect that not supporting Linux was mostly a business decision. Technically I don't think there's a ton of institutional knowledge around Linux on the product teams.
It's been well known internally that it makes an atrocious amount of RPC calls since the Carl Bass days. If I had to make a guess, I'd say that historically most of what you've seen with slow startup relates to authorization more than anything else. You could probably mitmproxy it if you really wanted to, the last time I checked they weren't doing any certificate pinning. Hell, at one point Little Snitch even wanted to know if I wanted to access a staging server.
