This is not as mysterious as you imply. DxO published a FAQ response to the problem of mobile-device RAW support here:
Support for RAW generated by smartphones – Help center
Admittedly, there is a little bit of “take our word for it” in this article. But it’s far more clear than the past situation of wondering why DxO isn’t taking more of an interest.
If an app is needed to obtain a Bayer RAW file, then it sounds like it’s being manufactured from processed data. DxO is very picky about where RAW data comes from, being true data from the sensor that hasn’t been put through a virtual machine of some sort. Unlike other software, as far as I know, PhotoLab and PureRAW perform denoising and some other corrections in the demosaic stage of processing. This represents a meaningful difference in how DxO can handle data that isn’t truly RAW.
DxO most definitely has explored supporting RAW files that lack optics modules. For example:
This might be useful for further reading and consideration:
And this:
I hope this helps.