I could be wrong, but I think this is a reference to some oversight where the ruby text for "girl" read "boy"...

http://dic.pixiv.net/a/%E5%A5%B3%E3%81%AE%E5%AD%90%28%E3%81%8A%E3%81%A8%E3%81%93%E3%81%AE%E3%81%93%29

yep, so she's meant to be male here

and yeah something about "traps dont have breasts" but that's how it is according to pixiv

On the tags used on his pivix image, the futanari tag is used and that I believe takes precedence.

Also removing the trap tag as one can easily see the penis in the thumbnail and also the character is a futa here and not a boy.

^ Nope, they're user-added tags.