Explain the atomic orderings used in race

src/race.rs

@@ -10,13 +10,14 @@
 //!
 //! All types in this module use `Acquire` and `Release`
 //! [atomic orderings](Ordering) for all their operations. While this is not
-//! strictly necessary, it is useful for users as it allows them to be certain
-//! that after `get` or `get_or_init` returns on one thread, any side-effects
-//! caused by the setter thread prior to them calling `set` or `get_or_init`
-//! will be made visible to that thread; without it, it's possible for it to
-//! appear as if they haven't happened yet from the getter thread's perspective.
-//! This is an acceptable tradeoff to make since `Acquire` and `Release` have
-//! very little performance overhead on most architectures versus `Relaxed`.
+//! strictly necessary for types other than `OnceBox`, it is useful for users as
+//! it allows them to be certain that after `get` or `get_or_init` returns on
+//! one thread, any side-effects caused by the setter thread prior to them
+//! calling `set` or `get_or_init` will be made visible to that thread; without
+//! it, it's possible for it to appear as if they haven't happened yet from the
+//! getter thread's perspective. This is an acceptable tradeoff to make since
+//! `Acquire` and `Release` have very little performance overhead on most
+//! architectures versus `Relaxed`.
 
 #[cfg(feature = "atomic-polyfill")]
 use atomic_polyfill as atomic;