Cefey, that's still not good for the OPT time builder. The fewer who continue through to instrument, multi & instructor ratings, the less dual that will be done as a proportion of the total training time budget. Instrument, multi & instructor ratings are damn near all dual training, unlike PPL level training.
It skews the ratio of dual:solo towards solo for that student. The end result is that even more students are needed per OPT time builder compared to a bunch of straight through CPL/ME/Instrument/Instructor students due to the reduced overall dual time and also the unfavourable* dual:solo ratio.
*unfavourable to the OPT time builder, that is.