Benchmarks are easily abused, misused, and misinterpreted. E.g., benchmarks looking at some very specific aspect of query performance being extrapolated to more complex/real-world queries.
Also trade-offs are rarely mentioned in benchmark numbers– e.g., great write throughput, at the expense of: ?.
It's fun to be cynical about stuff like this, but it's rarely as simple as "Ellison didn't react well to that and decided to forbid benchmarks".
Additionally there are safer, usually reasonable, ways to deal with what would otherwise be breaking changes. Give the changed functionality a different name, create a new namespace/module without the removed functionality, or create a new library if you have introduced something fundamentally different (e.g., w.r.t. how you interact with it). That way your users can choose to refactor their code to use the change, rather than discover their expectations no longer match reality when they upgrade.
I've been happily employed (and regularly solicited) as a Clojure developer for over 8 years.
There's no shortage of Clojure dev positions for developers that want to write Clojure.