With Tidal MQA pass through either on or off the 818 still displays 352 on 2L material so that makes me believe the 818 decodes to the maximum rate available and then repackages it using MLP for transmission to the DSPs as you said. The SEs recognize that rate and the legacy DSPs stay at 96/24. Strictly MHO.

Ken

Main: G68J, 5K2s, 5Ks, HSU subs, Pio 151FD, Dish VP722, Roku, Wadia I70, Anti Mode Dual Core, Oppo 103D Vanity Lite
Office: SBT, Berkeley Alpha DAC 2/MQA, Magico S3 Mk II, Boulder 2060, Lumin U1 Mini streamer, Roon.