Yep, Matthew, it does. Although if we knew nothing else about the scenario, it would be possible, but much less likely, for the children of a brother and sister--a daughter of the brother and the son of the sister--to also see approximate 50% xDNA sharing (about 77.5 million base pairs, or around 97cM). On the whole, the X chromosome undergoes recombination (crossing over) at meiosis in the mother with about the same frequency as a similar-sized autosome, Chr 7. But around 14% of the time, there is no recombination and one of the mother's X chromosomes gets passed intact (a single crossing over happens about 30-31% of the time, and two crossovers about 32-33% of the time).
If the common ancestor(s) is a father, though, it's a high probability that it's either the same man (the half-aunt scenario), or two full brothers (the 1st cousin scenario).
That the two matches Candice is working on share almost 170cM more autosomal DNA than the theoretical expected in either scenario (and about 155cM more than the average from the Shared cM Project) still makes me lean toward the half-aunt, half-niece possibility. All our genealogy testing and reporting companies work only with sex-averaged centiMorgan values but, using the broad averages from Harvard's David Reich, the female genome undergoes crossover about 1.7 times as frequently at gametogenesis than the male: around 45 crossovers compared to 26.
The net result is that, for recent generational distances, it can make a difference if we look at the cM estimates as male/female and not just as sex-averaged values. The mother will be distributing--again, very rough average--46 segments (including the X) to each child, while the father will be giving only 27, including a Y. The chromosomes are all the same size, though (discounting the sex chromosomes for the moment), so what will happen is that in the next, subsequent generation larger but fewer segments will come from the grandfather, and smaller but more segments from the grandmother. This is the root of the reason that, when we try to look at distant matches like 4C and beyond, we most often end up seeing more matches on the maternal line than the paternal. There are considerably more segments to spread around.
The half-aunt, half-niece scenario would have the same man as the common ancestor, with an extra generational step (birth event and meioses) on one side. This could explain the greater than normal autosomal sharing over a 1C possibility, and also fit with the greater number of segments typically seen in avuncular relationships as opposed to 1st cousins.
