Does MutableCallSite.syncAll actually work?

The documentation for the MutableCallSite.syncAll method appears to be 
quite thorough, and in particular: "In terms of the Java Memory Model, 
this operation performs a synchronization action which is comparable in 
effect to the writing of a volatile variable by the current thread, and 
an eventual volatile read by every other thread that may access one of 
the affected call sites."

https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/lang/invoke/MutableCallSite.html#syncAll(java.lang.invoke.MutableCallSite%5B%5D)

Upon inspection, I see that the implementation is quite trivial and 
somewhat old-skool with respect to memory barrier enforcement.

     public static void syncAll(MutableCallSite[] sites) {
         if (sites.length == 0)  return;
         STORE_BARRIER.lazySet(0);
         for (MutableCallSite site : sites) {
             Objects.requireNonNull(site); // trigger NPE on first null
         }
         // FIXME: NYI
     }
     private static final AtomicInteger STORE_BARRIER = new AtomicInteger();

Given the FIXME comment, which I assume means, "not yet implemented", 
does the syncAll method actually do anything? I don't understand the 
low-level details regarding how dynamic call sites get updated within 
HotSpot, but perhaps a simple memory barrier is all that's required? If 
so, that's great, and then I suppose the FIXME comment is wrong. 
Otherwise, this looks like a bug when considering the well specified 
documentation.