Many blu-ray players can decode DTS up to 7.1 channel and output it as multichannel PCM, so even if your A16 doesn't support DTS you may still be able to listen to that track.
Yes, like the Oppo players do if you set the HDMI audio output mode to LPCM. Then it would deliver PCM audio to the A16, and you'd be listening through a PCM room on the A16, not a DTS room. All automatic of course on the A16 which would pick the correct configuration depending on the arriving source format.
But as you say, in this case it would be the Oppo that would be doing the decoding of the original DTS-MA 7.1 audio, not the A16. If you set the Oppo to send HDMI audio out as bitstream, then the A16 would have figured out that it was getting a DTS-MA 7.1 source and treat it as a DTS room, which would require the DTS:X upgrade.
I have my own Oppo 203 and also a copy of the BluRay 4K UHD disc "Life of Pi" which has an English DTS-MA 7.1 audio track (as well as multiple lossy foreign language DD5.1. tracks). Since there is also an English "descriptive" DD5.1 audio track I'm going to guess there was also a "non-descriptive" DD5.1 audio track that probably would have been presented to me if I'd not been using an Oppo 203 which supports the DTS-MA 7.1 audio. Can't be sure. But there is no English DD5.1 with "non-descriptive".
Anyway, in planning my reply to your question I decided to explore for myself what exactly the A16 would do when I sent this DTS-MA 7.1 audio to it as "bitstream" (since my A16 is fully HDMI/firmware upgraded and license enabled for both DTS:X and Auro-3D). Turns out the experiment was a learning experience. Yes, it was of course accepted and decoded perfectly by the A16. But it was also "upmixed with Neural X", which upon investigation turns out to be because I had not enabled "DTS Direct" in the preset!
In fact I hadn't noticed that "DTS Direct" setting before now. But seeing "Neural X" as an active upmixer caused me to learn about it, and take appropriate action.
I am a bit of a purist, and don't normally want to listen to "faux audio" that is not what the producer originally created. So while I do appreciate the enjoyment afforded by Auro-3D's upmixer (which I agree seems to be the best of the lot) when only 2.0 PCM stereo is the source, I normally don't want to artificially further enhance native 5.1 or 7.1 just to feed sound to artificially simulated height and presence speakers that I don't even have and therefore never "really measured" for my ears into a real PRIR.
Nevertheless... I have now enabled "DTS Direct" on my non-immersive 5.1 and 7.1 presets, in order to disable "Neural X" specifically if I want to listen "as a purist" to a source disc with the exact audio DTS-MA 5.1/7.1 track that it might come with. However I have NOT ENABLED "DTS DIRECT" FOR MY IMMERSIVE PRESETS with DTS:X (9.1.2h), so that if I actually did want to listen to the Neural X 9.1.2h upmix of a DTS-5.1/7.1 MA audio source then I actually could.
