Well, at this point I don't think that my voice would change much but see me try (and fail) making the case
The problem with the red font is two fold.
Firstly, the moment people shoot themselves in the foot is different from when they are setting up things. This screen is encountered exactly once per installation as a finishing step. User is a bit unfocused and mentally strained, wants just to get it done. When the problem will arise, they most likely won't remember the message that made them a bit uncomfortable at the start.
On the opposite, the fail-safe checkbox looks like an innocent dove compared to the message. When you toggle it (just one click), there's no pop-up, no riddle to solve, no frames flashing pink, no nothing. Even though it is supposed to feel uncomfortable.
Secondly, about the design: it doesn't look right i.e. defies rules of design established in the rest of the app.
Here I'm not talking about the text itself, I think it's nicely put. It might be a good start for a curiosity driven post (Top 10 reasons why sync is not a backup). However, we're emotional creatures and the medium is often the message (c).
It looks as if you're running beta and a kind inside soul decided to sneak a note to user that everything may fall apart at any moment. And it's standing right below the "money-making" feature pressing uneven attention, tapping in uncertainty and generally creating a distraction at the place where there shouldn't be one. Of course we can't but it could be very useful to see A/B test on the conversion with or without this message.
Again, I understand it's just a suggestion and it may be revised to be a better version of "red font". But it still would be a warning message, not an asterisk.
— heck you too, so what do you suggest?
How about putting the text above the sync interval dropdown?
Most users will go there and most likely will encounter this page during problems. There we also would have more space to explain two-way sync nature and attach a link to more resources — the page is mostly empty if you don't open advanced settings.
Even if both GSOC docs project and packaged plugins will succeed, this little corner devoted to backup could still nicely educate users about how sync relates to backup showing off extra mile devs took to protect users' data.