So Apple seem to have either capped animation frame rate on the 6S+ at 30fps when GUI transparency is enabled or as with transparency disabled it runs at 60fps; which could likewise simply be an oversight / bug in iOS 9.
I imagine this one will be an easy fix compared to the other bugs in iOS 9-9.1 that persist.
Angela Griffins choice of naming the video as 'performance issues' was clearly just a 'device' to solicit more views and hence garner increased revenue on her channel. I'm sure if she simply labelled the video 'transparency animation bug on 6S+' it would not be as sensationalist.
There is always an ulterior motive (this occasion - viewers) and as I say whilst the issue / bug is real, as the solution (turn on reduce transparency in accessibility - contrast) proves that the device clearly is capable of running animations fine and dandy (and the myriad of games prove it can handle transparency and 60fps without hassle) - as I say I'm confident this is a bug and will be patched in the future, much like the TouchID issue many of you are having.