I had no idea that was a thing!  I now know ‘wantan’ is an approved alternate spelling of the pinyin (did some research because I love Google), but it looks like ‘wanton’ is just the sex thing.  And I think the issue comes in more when people talk about ‘moaning wontonly,’ which just.   ¯\_(ツ)_/¯.  I dunno, that always brings me up short and makes me ask Questions.