Voice Recorder 7 Pro was the program I first ran with the d:vice, it produced 96 kHz sized files with no info at all in the higher frequencies. I have allowed the app to update but not experimented for over a year. Just ran a brief test again with it at 96 kHz setting and in iZotope Rx7 it is clear that there is NOTHING above 23-4 kHz, it flatlines in the spectral analysis window. I am still using iOS 10 (afraid to break anything with an upgrade) so it is possible that VR 7 Pro plays nicer with the newer iOS versions, but I won't risk trying that as I can't go back to iOS 10 if something breaks.
I do not have Metarecorder, but when I questioned the DPA guys at the AES show in October about a 4 track version of the d:vice they recommended Metarecorder for syncing two MMA-As, since the power drain from a 4 channel d:vice would be more than an iPhone could handle. I did not ask them about Metarecorder at 96 kHz. It's on my list of things to maybe try, but I am currently busy learning Reaper so I can handle the 19 channel feed from my Zylia ZM-1, and this has maxed out my little brain for the moment. I have a voice and piano session Friday that I am getting ready for (stereo shotgun on the singer/pianist, omnis on the Steinway, with the Zylia as backup). I may play around with Metarecorder over the weekend, but we have three early instrument concerts to attend. I could also throw in something about the day job, but I'm retired.
Jeff