1. Since a full-factorial design was investigated, most presented figures are too oversimplified to catch the findings under each condition because only averaged values were plotted. Merely observing the summarized information may lead to inappropriate conclusion.
2. As the old saying, multiple imputation strategy (i.e., combing the results form a set of plausible values) is recommended to take into account the measurement error of person ability. The simulations, however, did not think of that.
3. Actually the concurrent estimation and later latent growth modeling can be conducted simultaneously in Mplus, and the derived results can be treated as the references.
4. I think the major contribution of this study is that the authors illustrated the performances of different vertical scaling methods under various conditions with limited data matrix.