The iPhone 6s RemoteIO Audio Unit appears to default to a hardware sample rate of 48000 sps. When my app requests a preferred output sample rate of 44100 on an iPhone 6s, the automatic resampling from 48k to 44.1k appears to be low quality and noisy (appears to adds a lot of spectral aliasing). Far more noisy than on any iPhone 6, 5s or earlier that I've tested using 44.1 ksps RemoteIO mic recording.
Is this a bug? Or did I miss some new setting allowing for a 44100 hardware sample rate or a higher quality sample rate conversion?