My theory is that it's actually a fashion thing in the era MA takes place in. Kind of like how it was fashionable in parts of Elizabethan-era Europe for ladies to show a bit of aureola peek above the bodice. "Naked" Edie doesn't have it, so we know it's actually part of the clothes, not her actual anatomy. Miranda has it, but her clothes look like they were probably custom machine made from a scan of her body, so it's arguably a deliberate feature on her part (no good reason why clothing that complex and fitted could have it as an error, especially since Miranda seems like the type who'd spend as much on a designer watch as normal people spend on a car).
Most MA clothes kinda look like they were made that way, actually, which is actually pretty cool IMO, in that racks and changing rooms in the clothing stores of the future could very plausibly be replaced with body scanners and fabbing machines.
The banshee vag doesn't bother me, because it's actually more realistic than barbie anatomy given the the banshee is a type of husk rather than a robot like EDI. Reapers don't care about sexual junk, and all husks are naked, so a female husk having a vag isn't weird unless the viewer has weird reactions to nudity. "Not bowdlerized" isn't the same as "pervy".
If the make husks had wangs, I'd be more likely to consider it BW being perves, since male bits are dangly actively extraneous things (for a husk) that would likely be lost/removed in the conversion process. Female bits are internal though, so unless there was a technical reason to give them a robo c-string, I'd expect the external opening at least to be to be just as present as, say, their navels.
That said, they do have dangly extraneous boobs (again, for husks) with robotically highlighted nipples, so... yeah...