Nah man, exit interviews aren't to express opinions or talk shit, it's a data source for HR to identify problems emerging as patterns and improve their org/company.
One guy saying "my boss sucked" isn't really feedback
One guy saying "my boss sucked" isn't really feedback
These are the same thing. You're trying to legitimize your opinion under the pretense of seeking raw, objective data, and characterizing OP's interview responses as something less than data, but it's not true.
Or maybe you've got some other data-points indicating this guy is an issue? Say, his projects are consistently late, or there's issues developing new features, or his teams have a higher attrition rate, or, or, or.
This is why it's my opinion that these things should be as secret as possible so people can feel comfortable voicing their real opinions knowing it won't blow back on them, and the company can get real feedback that might prevent thornier issues from becoming terminal.
It's 100% CYA and nothing more. A performative act so the personnel department looks like it's serving the business and complying with labor laws.
- My boss doesn't like me and excludes me. vs - I think my boss has a few favorites who get all the cool projects. Despite me being the best person as I had the most experience with technology X, my performance in good standing, and having showed interest in the project, I didn't get assigned to that project.