You're dealing with a Japanese company and Japanese women are considerably more adamant about their clothing being form-fitting and as slim as possible. Japanese women in general will not buy bulky clothing. MontBell is just catering to their demands. MontBell is also divided between two branches, the trendier "MontBell", and the more technical "Zero-Point" line, in which women's clothing is spec'ed the same as men's.
PS. Japanese women in general are much colder than western women (anemia is very high in Japan) so it would make sense for them to want warmer clothing, but visit any Japanese outdoor store and the women's clothing is always much slimmer and thinner than men's. They do tend to do lots of layering with thin layers (which actually makes sense. When Mallory's body was found on Everest a few years ago they found that his clothing was much less bulky than modern counterparts, consisting of many thin layers, and actually much easier to move in. Researchers have found that his clothing was perfectly appropriate for Himalayan climbing).
PPS. If women and men outside of Japan want to have more of certain types of clothing from MontBell perhaps I can suggest what Japanese, men and women, are always forced to do with popular US and European brands here that invariably don't fit them very well: officially contact the company in question and work with them and distributors to develop clothing and shelters specifically designed for your needs. Fifteen years ago Marmot, The North Face, Patagonia, Mountain Hardwear, Aigle, Haglofs, Scarpa, Zamberlan, Lowa, Jack Wolfskin, Fjell Raven, etc. were impossible to find in Japanese sizes and Japanese outdoor enthusiasts were very frustrated with the lack of choices. So they worked for a long time to develop models that fit the Japanese sizes. Now I have problems finding pants and shirts that fit me, but Japanese are buying those brands in record numbers!
Japanese being Japanese I'm pretty sure that MontBell would be more than willing to work with the US market and customers (after all they specifically designed and built certain shelters that are only available outside Japan) in developing clothing for that market. I don't think these online reviews are going to make much of an impact in changing MontBell's design plans, since Japanese are much more respondent to workable solutions and direct correspondence than public criticism. And you have to remember that in the mid-90's, when MontBell first tried to enter the US market, they were severely burned by a number of US distributors who made big orders and then didn't pay for them. MontBell had to close its stores in the US and start again. So they certainly don't trust Americans yet. Until that trust is firmly reestablished probably they are going to be very careful before putting out lots of designs that won't sell in Japan.
(Yes, I've been using MontBell product for a long, long time (since 1977), have used a LOT of them, and no, I'm completely unaffiliated with them)