It looks to me that is just because on Windows files representing shmem objects go into
C:\Users\<user>\Temp\shared_memory-rs
and on Linux into
Once I forced the Windows/Wine process to create a file in Z:\\dev\\shm, which in Wine corresponds to Linux's /dev/shm, sharing seems to work fine.
What do you think of a new wine feature where windows.rs get_tmp_dir() would just return Ok(PathBuf::from("Z:\\dev\\shm")) ?