That’s been rumoured for a while and there may be some truth in it - but to be fair it’s not beyond possibility that Apple being Apple have put weird ingredients into their RAW recipe and don’t share nicely with the other kids in the playground. It certainly appears that some proprietary Apple algorithms are applied to Apple ProRAW so it is not a truly ‘standard’ DNG format. If it was, it could be processed in any RAW editor (other than DxO of course!) without having to compensate for exposure extremes, etc.
The thread Support for Apple iPhone 12, 13 Pro, Pro Max files - #25 by ralfieri
alone shows 5.9k views - compared to maybe a few hundred for other popular topics - which says it all ito the need for Apple and DxO to address this customer concern. TBH I don’t see Apple giving a monkey’s, but I know a few people who are holding back on either buying or upgrading DxO because of the lack of support for iOS.