From michael.paik:

Per SERVER-14703, setting snapshot on a cursor doesn't prevent it from omitting documents in the resultset that are updated during the lifetime of the query, they only prevent dups. As such, the 'or objects missed' language needs to be changed. The parenthetical '(if an object is new during the query, or deleted during the query, it may or may not be returned, even with snapshot mode)' should become a first-class sentence something like 'If an object is created, deleted, or updated during the lifetime of a query, it may or may not be returned, even with snapshot [set to true (or lang-specific equivalent)].'