Yes, I'd think the analog output of the dac chip exits via 'evil' LTP containing opamps, but a quick check of the datasheet reveals that the ability to disable the digital filtering is built into the dac chip.
I take it that you're drawing no distinction between analog and digital filtering? I made no comment on the digital filtering, opamps are decidedly analog in nature from where I'm standing.
Regarding your assertion that Marshall says 'there's no ambience retrieval', what was actually said is -
So your takeaway from that quote is that the Ear Acute III given its topology is incapable of ambiance retrieval. Having lived with the Acute and also having the pleasure of hearing Dan Wright's excellent modded Sony, which IMO offer excellent ambiance retrieval, I assume that the last line is a caveat, and perhaps the recording itself lacks the ambiance.
Fair enough that the recording may well have been lacking. My takeaway wasn't what you're claiming it was though. Try again?