We can conclude that Ocaml outperforms GHC on this edge case for the GC.
There's nothing to conclude here about a general case, and it may not even be possible to make general conclusions about GC.
Exactly my experience of the Java JIT and GC where I worked on uh "optimizations" of related metrics in two or three projects.
Just a casual observation of the commento-sphere after a lay imperative programmer's cursory research of functional programming. This post, sample-of-one hugely notwithstanding, seems in the absence of counterpoints to suggest that, as potentially narrow as the benchmark may be, Ocaml has some very strong arguments against Haskell on the compiler implemenation front.
I can't help but wonder if this GC outperformance is the flipside of the coin of Ocaml's much maligned lack of multi-core capability.