4K HEVC not Direct Playing with update 1.19
I've updated my PMS to version 18.104.22.16829 and my Apple TV to version 1.19. The changelog for 1.19 states that HEVC Direct Play is now supported, but my PMS is still transcoding 4K HEVC in a Matroska container to H.264 and destroying my server's CPU.
Is 4K HEVC in an MKV container still unsupported for ATV4K?
Some clarification on this would be great, thanks.