"So some modern dacs can easily handle DSD and PCM formats natively, while others can’t."
Sony has had the patents for DSD locked up since it's inception and the vast majority of the DAC chips available for the last couple of decades have incorporated PCM up to 192 Khz as well as DSD capability all the way up to 512 when it became available. The issue requires licensing the use of the format available incorporated in the chip and implementing it in a manner the licensing allows.
"I went to the dac specification sheets to try to discover why. That’s when I discovered the Burr Brown specification sheets made no mention of DSD."
Probably just the particular chip's data sheet you looked at because TI would not let it's pants down and not be competitive in that market segment.
"DSD audio is down-converted to CD quality audio for analogue playback."
SACD is a multi-format medium from single layer SACDs that will only work in players capable of decoding them along with Super Audio CD that contain multiple formats on a single disc and are designed to be backward compatible with all CD players and not requiring any "down conversion" whatsoever. Just look at the labeling on your SACD's packaging.

