Their solution is to act as a proxy between your HomeAssistant installation at home and the public internet. Supposedly the SSL certificate sits on your device and they have no access to your data. I think this is the right way to do it
> It's documented how to set this up yourself if you don't wanna pay them to manage it for you too.
That right there is the best way to go. Everything in the open, everything can be self-hosted, but you can pay for the convenience of someone else doing it.
I’d normally have done that myself. But considering that having them handle it also funds Home Assistant development, it was actually pretty easy to decide for.