I don't know whether VBA2C vs. VBA1C makes a difference, but we do have studies showing that VBAC labors tend to be longer compared with women who birthed vaginally the first time. Here is one, and here is another. I can think of both psychological (increased anxiety, for ex.) and physiological (women with prior c/sec would be more likely to be women who progress at a more leisurely pace, for ex.) reasons, but the take-home pay is that clinicians should expect VBAC labors to progress more like 1st labors than labors in women with prior births.