About 1-2 months after the WEB-DL, the physical 4K Ultra HD Blu-ray releases. A "Remux" takes the exact video and audio from the disc and places it into an MKV container without re-encoding.
If your reference to "mkv new" relates to technical issues with media files, recent community discussions on the MakeMKV forums indicate that some users have experienced difficulties ripping the 4K UHD discs of the film, suggesting that specialized hardware or software updates may be required for certain physical editions. Review: 'Ballerina' - The Daily ballerina mkv new