it's a rendering error. a crash is a catastrophic failure. non-catastrophic failures can include failing to load or discoloration. I had an error a couple weeks ago while doing WHM quests. they toss a glowing ball of energy at you. i got a square and the game crashed immediately after the CS. these things happen now and then. but they have a higher rate of occurance for FFXIV due to inefficiencies in the coding etc.

packetloss can also impact this. the SE server is telling your PC what to load. if it's losing half the data your PC doesn't know what to load so it just doesn't load anything.