Explain to me the upside of honesty.
but can definitely see risk and downside
And this is the problem, in my opinion. People are being dishonest with themselves and others, promoting bad work environments, all due to fear of imagined consequences.
The exit interview is unlikely to be read by the audience to which you seem to be referring (or at least, read in any serious way). By the time you've left, the only meaningful feedback to leadership is attrition.
You're removing an important piece of context: there's no upside to honesty in an exit interview.
Wrong. As others are pointing out, by stifling your honest feedback you're harming the company and your now-former coworkers.
All because you fear a hypothetical situation.
...and? So what? What's in it for _me_?