TemplateTable::fast_aldc compares the just-loaded reference with Universe::the_null_sentinel. If it really is that null-sentinel, we may get a false negative (with GCs like Shenandoah that allow both from-space and to-space copies of an object to be around), and thus skip NULL-ing the ref. In other words, it would allow to get the-null-sentinel out into the wild as oop.