I think the original commenter confused taking the CUBIC implementation from the kernel and rewriting that in Rust for use in their QUIC implementation or they

I think the original commenter confused taking the CUBIC implementation from the kernel and rewriting that in Rust for use in their QUIC implementation or they just jumbled their wording. It does make sense to use an existing battle tested implementation of a congestion algorithm because there are potential many real world failure modes that you might not anticipate if you try and write an implementation from scratch.