Like a lot of things, Die Cast collecting has its own terms unique to the hobby. Typically, they have items such as rubber tires, which can be removed from the car. These are not suitable for small children due to the choking hazard.
Some manufacturers produce toy-store quality cars that are intended for the small ones.
Also, cars that have Alcohol or Tobacco sponsor logos are classified as adult collectibles for obvious reasons. In fact, I have seen disclaimers on some packaging indicating that they are not to be sold to minors. Any Die Cast an adult collector buys. No, they are not toys. The fact that they can be found in the toy aisle is not significant.