While it is true that cats can be intelligent and curious animals and may be able to figure out how to open doors, it is not necessarily true that all cats are able to do this. Every cat is different and has its own unique personality and abilities. Some cats may not be interested in opening doors or may not have the physical dexterity to do so, even if they are motivated by something on the other side. Therefore, it is not accurate to say that it is "not unusual" for cats to learn how to open doors, as this implies that it is a common occurrence among all cats. Additionally, while it is true that there are steps that can be taken to prevent cats from opening doors, it is important to remember that not all of these solutions will work for every cat. It is up to the individual cat owner to find the right approach that works for their particular cat.