Ok, if want see what carbon build up and IMO lack oil changes does too turbo/direct fuel injection engine does to piston rings. Here good video.
https://www.youtube.com/watch?v=VhR2kMIr3NA
IMO GDI turbo engines may be new junk engines surpassed 1980s designs. IMO engine with fuel injection going down intake above valves don’t have severe carbon build up due to valves getting sprayed by fuel mist going to combustion chambers.
This Is My opinion I would not skimp on oil changes intervals with GDI (direct injected) engine especially With turbo which generates more heat and pressure on top piston ring groove.
IMO 2017 vehicle not that old to have major engine damage (but don’t know history?). By all slug buildup IMO looks like oil change intervals was too long? This all my opinion others may have different opinion which will probably not change mine.