You may have missed that classic 2-wire analog telephony interfaces are also connected in that way, eg. Si305x PROSLIC is what you typically see being connected to the digital audio signals of such a SoC “in the wild”.
Also the use of such SoCs in (audio-driven) home assistant devices or smart speakers is thinkable, though not likely as most of the chips nowadays for that got at least DSP features, if not even NPU for wake-word recognition and such (MT798x got none of that).
Also pro-audio application seems unlikely due to missing IEEE 1588 Version 2 support which would be needed for DANTE.
It makes sense now that you mentioned that telephony interface. I think those CPU cores (even the A53) are powerful enough for some DSP algorithms like word-recognition, having SIMD instructions helps. But Idk if it’s a common thing to do on linux