When it comes to how MQA MAY [and I will again emphasize MAY] be fully decoded within a full Meridian DSP system... I think it can be instructional to look at what the Explorer 2 does when used with the Tidal app.
If you use the Tidal app with Exclusive mode on... but Pass Thru MQA off... then the Tidal app will perform the 1st stage decoding out to a max of 24/96.
That 24/96 stream is then passed to the Explorer... which in that scenario becomes what MQA call a "Renderer".
The Explorer then performs the 2nd stage unfolding... resulting in up to a 24/192 file being fully decoded.
I think it's possible that the same logic may be followed by a full DSP system... with e.g. the 818v3 doing the 1st stage MQA decoding / unfolding up to 24/96... with that 24/96 stream being passed to the DSP SE speakers to perform the 2nd and 3rd stage unfolding up to 24/352, for the files which offer 8x rates.
It's probably no coincidence that the stream from the 818 to the DSP SE's is STILL the 24/96 stream preferred for many years by Meridian, thus simplifying the whole Player to DSP cabling etc.
We all know how long we've been waiting for the promised 24/192 upgrade from Meridian [never mind a 24/352 one]... so this method of dealing with MQA streaming allows Meridian to use existing Speakerlink cabling... and any requirement for new cabling or connections to deal with a 24/192/352 stream from the 818 to the DSP SE's is avoided.
Please remember that everything written above is my opinion only... with no insider information... and Meridian may well be doing this in an entirely different manner