Even if it was, it likely was tuned for, or even built for, only one OS for years.
That will have made an impact. For example, if thread creation is faster on an OS, starting threads for smaller tasks becomes a win; if locking primitives are slower, it may be better to take a full-table lock more often.
That will have made an impact. For example, if thread creation is faster on an OS, starting threads for smaller tasks becomes a win; if locking primitives are slower, it may be better to take a full-table lock more often.