The claim made by Kyle is not entirely true and unjustifiable because for the figures or solids to be similar, not only the corresponding sides should have the finite ratio but also the corresponding angles should be equal. Although, the claim depends on the type of quadrilateral.
Kyle's claim is incorrect. This is because the square and the diamond are not the same shape. If they would be the same shape, but different sizes (provided the ratios of the corresponding sides are equal), then they would be similar. But they do have the same corresponding side ratios, so they could have been similar if their shapes would be the same.