What? This is simply just a coincidence. Like the OP explained the store doesn't have a maternity section and they just want the layout to look proportionate.
People just want to complain about anything and everything.
Womenswear and menswear are categorized differently. You'd be surprised, the sizes that are available for men are generally plus, that's why they need "slim fit" to adjust the sizes to smaller men.
Men naturally have plus sizes, like 3-4XL already. They just aren't called that
Then women shouldn't be called that either. In fact, women naturally carry more body fat (e.g. estrogen levels), so it really doesn't make sense to act like a larger framed woman is unusual.