Simple is not the same as non-obvious, so no, it's not the term used in patent law. Something is obvious if a non-inventive person skilled in the art _would_ have performed it through routine steps (at least here, some of the mosaics I see coming from the US are batshit insane and no sane person would have used them to come to same result the examiners is claiming - that said, this is a practice that is in favour of the public, it requires the applicant to reduce the scope of the claims further which leads to smaller monopolies).