HDCP 2.2 was relatively recently introduced and is a requirement for 4K protected media, e.g UltraHD Blu-Rays.
I have not found a definitive statement as to what version of HDCP Macs support but would presume it is still less than HDCP 2.2. It maybe that adding support for a newer version requires a hardware change, for example a newer video chip.
Since Apple themselves do not provide any 4K media via their iTunes Store, do not support H.265 as widely used for 4K media and do not support even Blu-Ray I would not hold ones breath.
Note: This does not change the fact that Macs do support HDCP for use with an external display for normal HD media and this does work for movies from the iTunes Store and Netflix. No idea about Vudu since it is one of those esoteric things only a handful of Americans have, here in the civilised world it does not exist. 😉 (Same applies to the equally esoteric Hulu.)