V
typealias AnyObject
, сделали для удобства, обсолютно одно и то же
This proposal merges the concepts of class and AnyObject, which now have the same meaning: they represent an existential for classes. To get rid of the duplication, we suggest only keeping AnyObject around. To reduce source-breakage to a minimum, class could be redefined as typealias class = AnyObject and give a deprecation warning on class for the first version of Swift this proposal is implemented in. Later, class could be removed in a subsequent version of Swift.
Где в альтернативах уже сказано о
An alternative solution to the class/AnyObject duplication was to keep both, redefine AnyObject as typealias AnyObject = class and favor the latter when used as a type name.
А так как уже во всех примерах в документации только AnyObject, то могут добраться когда-нибудь и до выпиливания class, что логично. ;)