A caution period is not the same as a yellow flag. Yellow flags are in the game, the AI just pays no attention to them and they rarely come out due to AI cars teleporting to pits as soon as they crash.
To add a safety car to the game would require a **** load of work that is much better used making what is currently in the game work properly. The safety car would add nothing to the game, as it'd just force everyone to stack behind it, and make a pit stop, just like when a safety car comes out in F1 games. Then you have to sit behind it for ages bored out of your mind not racing in a racing game. Safety cars are great for safety in real life, but in a game they are boring.
I have never seen the safety car being referred to as a caution period in F1 or any other Euro motorsport. Only in American series have I seen that phrase.
Seriously, you're asking for a feature that would take a lot of work and add sweet fa to the game, when there are about a million things that need attention before that...