The team had partitioned their work into two steps considering that meso-lactide can be determined by GC where at the same the other two compounds can't be separated on the GC column, then they used HPLC. So, HPLC is used as an essential supplementary method and not for comparison as you said and I have never heard before that a team works in chromatography do such a comparison between GC and HPLC performances even when you analyze pesticides. At last, absolutely they consumed a long time in the separation and quantitation!!