Intel made significant changes to their video encoder/decoder engine in the latest Xe implementation:
From
https://www.tomshardware.com/news/intel-rocket-lake-release-date-specifications-performance-all-we-know:
Intel's Xe graphics also bring in-built AV1 decode acceleration, which is helpful because the codec reduces bandwidth up to 20% for video streaming (such as 4K and 8K content). Rocket Lake also features Intel's 'new' Always-On QuickSync Video. This feature allows Xe Graphics to run concurrently with a discrete GPU so you can offload some workloads, like video streaming with QuickSync, to alleviate the burden on your discrete GPU. This feature has already been around for several years, but it required BIOS support, and you had to manually enable the integrated graphics unit after you installed a video card. Intel says the technique is now a supported and validated configuration that's enabled by default in the BIOS
They don't say anything about h.265 but it is possible that they are keeping it as a last minute announcement. What is super useful is to be able to enable both QuickSync and nvenc at the same time.
In the past, DVR would crash if I enabled both QuickSync and NVidia decoders at the same time. However in 17.1 beta 10, I am able to select both under Preferences->Decode Options and it no longer crashes. May be a sign that BlackMagic worked on this QuickSync concurrent processing.
I did some render tests but on my Gen 4 QuickSync cpu there is not much to prove/test.