The claim that lipid-soluble and small passive molecules diffuse directly through the phospholipid bilayer is a fundamental biological principle supported by general scientific knowledge and membrane transport studies.
The claim is a standard, well-established biological fact regarding membrane permeability and simple diffusion. Although many retrieved papers deal with materials science, drug delivery, or specific nanoparticle/protein interactions, paper 6 supports the concept of passive transport directly through the phospholipid bilayer for water molecules.