I'm running Premiere 2019 on a Macbook Pro 13" 2018. I Have 4K HEVC 10bit files which playback smooth and fine in Final Cut, Da Vinci Resolve and in the Quicktime player.
Unfortunately in Premiere, however, the playback is very slow and unresponsive. My educated guess is that most software is using Intel's hardware HEVC decoding but Premiere isn't.
Is this a known issue which may be sorted in a future Premiere version?
We have been focusing more cycles on improving performance for H264 and H265 and will continue these efforts.
There are many different flavors of these formats and also many different chipsets with varied functionality.
We're definitely continuing efforts to improve performance in this area (and others)