nice

maybe better to move the topic to " Miscellaneous "

Pretty obvious ---  it's a solution (splitting the modulator and DAC) created for the audiophile community. The chip is super expensive, and simpler solutions can do the work very well already.
and there's no reason for RME to spend time in this architecture and/or performance hype rather than more important/unique RME technologies.

AK4499EX (which only does dac conversion, not from PCM/DSD, but from a modulated coding) needs to be used together with AK4491 (which does oversampling and sigma-delta modulation).
They were derived by previous product AK4499EQ. I would assume the former two chips cost even more than the latter.
Before the chip crisis and the AKM fire, AK4499EQ cost ~$80 per chip, while AK4493EQ cost $5 per chip.

Audiophile manufacturers may be interested in investing R&D resources on it to cater to their audience. RME certainly won't even care about it.

I don’t have any affiliation with RME but MC has repeatedly rejected ideas about using a better, premium grade chip here as it does not fit RME’s businesses model.