The definitions of leotards and one piece swimsuits is so minor they are indistinguishable without clear context. While the leotard wiki page helpfully points out that its "Not to be confused with" one piece swimsuits no further differentiation is made on how its different. The swimsuit wiki also directly refers to the leotard:
The classic one-piece swimsuit resembles a leotard, covering most of the upper body and crotch, usually with the exception of the back and upper chest
So what is the deal? I do find the section about the cutouts interesting. Is that it? Unless its obviously a swimsuit or has the cutout its a leotard. Or is it just the swimsuit requirement. So unless obviously used for swimwear based on context its assumed to be a leotard.
It's also worth noting that there are over 600 posts marked as both swimsuit and leotard, nearly 400 of them as specifically one piece swimsuits.