I believe you are right at least on the point of "Gnd in xlr should always be to chassis".
Our discussion here, however, is on XLR-RCA adaptor having "Pin 3 to ground"; is it just possible higher distortion/noise/ground-loop-hum, or also with "possible" harm to DAC and/or amplifier? I have a memory of reading about "possible harm", but I cannot remember the exact source(s) or web page(s) on that.
The further discussion on this issue is beyond my knowledge and understanding. I would like, therefore, to entrust expert people in audio signal handling for further discussion on this issue, please.
I did that. I ordered 10Vrms on xlr outputs 1 and 2 so I could bypass the buffer stage of my Purifi Eigentact and still have enough voltage to drive it to clipping. Was around $40 if I remember rightly.