No, it was not a typo. The subject is actually quite complicated. We need to make a tutorial on this.
With White Strong & Flexible you can build walls of 0.25mm thick. The problem they are not very strong. Just imagine two cubes of 2x2x2 cm connected together with a bar of 5 cm wide and 0.25x0.25 mm thick. If you pick it up it will most certainly break. Let alone that we have to ship it to you. That is the reason that the common statement is 2-3 mm.