I found this topic, where the issue of microintervals was discussed:
My takeaway is that it is up to me to decide if MB microintervals is something that will be beneficial for my training, because the algorithm seems to care more about time-efficiency and filling the buckets than about giving me the best workout in a traditional sense. Which is a pity for me because I don’t know anything about training and was hoping Xert would do all the thinking for me.