I had seen Your inquiry, as nobody replied, yet, here is my 2 0,02€ !
The resolution change is "per App". If there is no request from Netflix App to change it (remember you have to wait for the streaming to adjust to 2160), than, no there is no other settings in the NSATV, unless changing resolution to 4.2.2. bt2020 4k 59.95.
Nb: Oreo is coming in a while, maybe this will be sorted out!
Marantz Sr7011, Galactron Mk10b, Pioneer VsxLx50, Behringer NU3000dsp. Klipsch Cornwall, Wharfedale 9.1, Klipsch CP-6, 4xJblCS1214 in 2 double boxes, V.B.S.S. with Dayton PA460-8. Sony UbpX800, Lg Up970, Nvidia Shield ATV 2015, FireTv 4K, 2 Onkyio Dolby Surround ES600 pro, 2 Anleon MX200 Minimixer, Hisense 55M5500. 110 inches rolling screen, excelvan cl720d.