they... just look like briefs?
briefs and shorts are both very common underwear choices for guys
Although both are common, it's not originally the underwear choice given to the boys prior to when this was reported. (see second image from @gooochyeee for clarification on what it previously was)
It's really not a major issue, but still worth reporting just in case EA isn't aware that this has changed.
@mightyspritesims @rory_nutt The reason this is a 'bug' is that the underwear isnt tagged for male children, and is the 'female' one, if I remember correctly before this bug started the underwear was prevented to be on male children (even with the tag removed) but that was changed leading to this bug. Aswell as all thumbnails that showcase male sims in underwear are the orginal male one.
This was said to have been fixed in a earlier patch, but it wasnt actually fixed and thats why theres two posts with the bug template
@gooochyeeeIt's odd that this is being brought up again now specifically, as the tags for this item are Female/Feminine and Allow For Random DISABLED. While it is not Gender Restricted, I don't see how this specific underwear could appear randomly on any male child sim.
I assume the reason it's not Gender Restricted is because, as @mightyspritesims correctly says, boys and men wear underwear like this and blue is consumerism for boys.
It's a PartFlag issue. EAxis didn't want to clone the item and make "boy colors" and they didn't bother to flag it properly. Swatches can be flagged independently of each other but I believe that leads to other issues.
THE ONLY WAY to see this in CAS is to swap the Fashion Choice filter or activate both. It is the equivalent of doing the same with YA or older sims and seeing opposite "fashion choice" items.
In other words, this is a non-issue as it's currently configured. (And yes, I did just verify these tags in S4S.)
EDIT: Also, because this specific swatch is AFR DISABLED while the "girly" swatches aren't, even girls won't have it randomly assigned to them in-game. From this, I think it was mean to be a standalone boys recolor. I'll be fixing that AFR flag in my BG PartFlag Fixes.
UPDATE #1: See my followup reply at #13. @gooochyeee is correct, there's an issue here and it has to do with the DefaultForBodyType. The CAS items are correctly flagged but the game is apparently ignoring them and applying the DefaultForBodyTypeFemale item to boys (per UPDATE #2, the issue is more complicated than this).
UPDATE #2: See my followup reply at #16 for my findings. Cheers!
