It is a bug, games have bugs in them all the time, some are more noticeable than others. You understand that games nowadays get patches and updates because developers are not aware of every bug and glitch that are in the game, right?
I am not trying to defend games having bugs, but this is a small visual bug, it is not making your car drive through the ground, or crash into an invisible wall.
The great thing about games today are that people can post bugs and glitches online, or report it to bring awareness to developers.
Sorry for the lengthy post, I just dislike when people take a small issue and use it to make the devs seem lazy.