babie_lato
As I explained when I posted the chart with the different configurations, "mixte's" are originally universal utility bikes for any and all, they were designed for everybody, not as a women's bike.
Later high end one's are just that, high end mixte's not really racing bikes per say but when they got popular the companies jumped on the bandwagon and made very nice ones for those who wanted fancy, high end ones.
This frame is awesome, the seller is somewhat correct about the wheels as this one has posts for cantilever brakes and clearance for big tires and fenders, you might get away with 25's looking ok but if there's too much clearance it may not look right, this is also a stout frame and maybe on the heavy side negating the "magic" of lightweight tubing like 531. I would be inclined to go with this anyway and work through the process then you would be ready when you find a frame that you really want.