Ho approfondito, giusto per mia curiosità, e ho trovato un vecchio articolo su flatpanelshd che gira intorno alla questione. Ma fra i commenti quello di tale Geoff D mi pare avere molto senso. In breve, aggiungere il DV a un disco è ben più complesso che non farlo per uno stream.
Peccato!
https://www.flatpanelshd.com/news.php?subaction=showfull&id=1519123680
In case anyone wasn't aware, it's much more technically challenging to implement DV on UHD disc than it is for a streaming version. This isn't FUD, this is FACT: there's a mandatory requirement for all UHD Blu-rays that feature HDR to include an HDR10 version as well as whatever optional version (DV, HDR10+, Philips/Technicolour) is being deployed. Two separate 2160p encodes of reasonable bitrate onto one disc won't go so they devised a dual layer system, the 'base' HDR10 layer 3840x2160 10-bit HEVC stream and an 'enhancement' Dolby Vision layer contained within a 1920x1080 10-bit HEVC stream. The DV stream is not a readable video layer as it's merely a transport which contains the 'difference' data between the 12-bit master and the 10-bit generic layer as well as the payload of dynamic metadata, the Dolby processing then takes these two layers and rebuilds the full 12-bit DV signal at the display end (with more post-processing being pushed back towards the player with Sony's "low latency" DV profile).
"Okay", you might think. "it's a bit more complicated than a single stream OTT delivery, so what?". But DV on disc doesn't just have to contend with this dual-layer authoring, it's also got to contend with the specifics of how this content is physically encoded to disc, namely the dual-zoned High Transfer Rate/Default Transfer Rate portions of the 33GB layers. In order to use the maximum 127.9 Mb/s bitrate for the transport stream the discs need to be spun faster but in doing so the RPM exceeds noise limits in the inner 8% of a disc, so that inner 8% is restricted to a lower default bitrate of 108 Mb/s max while the outer 92% is able to use the highest 127.9 Mb/s max.
For a 66GB disc this isn't so tricky to manage but for a Triple Layer 100GB disc you've got to contend with a possible dip in bitrate at the second layer break where it changes from inner to outer (the pickup having read inner to outer for the first layer, 1st break from outer to inner for the second, 2nd break from inner to outer for the third) and if you're wandering into that inner 8% again then you need to be aware of this bitrate restriction during a key portion of your movie (anywhere between 1hr30 and 2h+ depending on the length of the film) whilst being careful to maintain optimal bitrate for your two HEVC streams (plus audio of course) as mentioned above.
Long story short: DV is much simpler to encode for streaming delivery but a MAJOR pain in the ass to encode onto disc and not all authoring houses have been certified to deal with it, e.g. Deluxe only just got certified late last year whilst Pixelogic (who bought a shitload of disc authoring IP from Sony) have been handling it for most clients from the start.