Just my $0.02.. there is yellow and there is warm. Across all products.. from iPads to iPhones to Macs.. I have had iPad screens that are cool and screens that are warm. I recently went though a LOT of testing with 2015, 2016, 2017 13” & 15” screens. Regarding your case, when I was comparing the 2015 15” and the 2017 15”, the 2017 was a bit more warm. It did not look yellow. Between the 2 I liked the 2015 more as it wasn’t too cool.. but the 2017 was more accurate IMO.
This is normal with panels IMO.