Howdy! Reporting a very similar bug elsewhere. I created my account to post this and it doesn’t look like I can create a new topic. I’m a complete beginner at this game – literally been playing for a couple of hours. I’m still going through the tutorials, and came across grass throughout the taxiway at KSEZ in the Taxiing tutorial. I have yet to even take off on my own!
Grass at the taxiway during the tutorial is pretty jarring for a beginner, I tell you. 
I’m running DX12 (BETA) MEDIUM at 2560x1440 on a Radeon RX580, msfs version 1.26.5.0 i believe.