[noggin]

The exceptions are LG and the 2019 Panasonic’s OLED’s that get the full Monty - TV led - DolbyVision treatment, and they also produce superior DV picture output as a result. 

What's the basis for that ? Isn't the difference between player-led and TV-led DV just the different routes that metadata takes? In TV-led (which is backwards compatible with HDMI implementations that otherwise only support static HDR metadata) the DV metadata is 'hidden' in the active video signal through tunnelling (which means the TV has to process the incoming video via DV-aware hardware to detect and extract the metadata), and some players may also have to be able to embed the metadata within the active video (presumably whilst it merges the dual HDR10 and DV enhancement video streams?).

With player-led DV the metadata is extracted from the DV video stream (or enhancement layer in dual stream UHD Blu-Ray ?), in the player, and sent separately over HDMI using HDMI's dynamic metadata pathways that were added in later. As a result the TV has no requirement to process the HDMI video signal to extract the metadata, as it is supplied using HDMI standardised signalling pathways (rather than using a tunnelling hack?)

What aspects of player-led vs TV-led metadata introduces a quality difference for the two routes? Or am I missing something obvious?

AIUI TV-led DV was always an interim system Dolby introduced to bypass the lack of progress in HDMI supporting dynamic HDR metadata?