That's interesting. High ISO purple shadows has always been a problem with my Nikon D800 and D810. Surprisingly difficult to correct with split toning without affecting other areas or general color balance, even with fine tuning the balance slider. Often I need to go to Photoshop to fix it.
It seems less of a problem with the Sony a7r II, but this is still the kind of functional upgrade that makes a new process version very worthwhile.
I don’t make a great use of negative dehaze but where shots already include fog/mist or perhaps a sunset shot the results seem much better with P/V5 compared with P/V4. The slider also seems to produce a much smoother effect.