If you look at steps 5 and 7 in this installation guide https://www.ikea.com/us/en/assembly_instructions/vidga-corne... you'll see that they have a way to tell you to use one screw vs another, but it's also true that Ikea's instructions aren't foolproof. This is just one example of how they really need to continue testing and improving their instructions because clear instructions are hard, and writing instructions without text is just making your job of communicating information that much harder.