This has been around for so long I think "playability issue" would be more fitting than "bug". Pretty much everyone who wither needs a fps boost or who wants to conserve battery power on their laptop has run into this at some point. As the screenshots below, show, a 4-chunk render distance in the overworld gives the player a clear view of their surroundings, and near the edge of the loaded chunks, the world rapidly fades into the distance fog. The nether's clean air-distance fog boundary is a lot less pronounced than in the overworld (is this a bug?), meaning blocks which whould have been clearly visible in the overworld are significantly dimmer in the nether. Not only does this make flying through the nether a challenge, but in survival it means ghasts can pound the player with impunity, knowing the player can't see them.

TL;DR: Just look at the screenshots.