I've had a look online. The binders and tuck-friendly swimwear is only sold in adult sizes. The video claiming otherwise misrepresented the situation, describing an adult swimsuit as being from the children's section. (It might have been found there, but that doesn't mean it was meant to be there.)
I object to the child and baby clothing with statements like "gay" and "queer" on them. Children aren't aware of their sexuality until puberty and labelling them beforehand is inappropriate because no one can predict the future. We don't put kids in clothes that say "straight", so this isn't about being homo/bi/transphobic, it's about respecting a child's right not to be sexualised at a young age.
In principle, I support genderless clothing for prepubescent children because there's nothing wrong with a boy liking ponies or a girl liking trains and there's no substantial body shape difference at stage of development. Clothing at that age should all be in one section marked "children's". The Pride collection fails in its execution by giving genderless clothes a different and equally pointless set of labels. Labelling the clothes as "non-binary" or "trans" or "queer" is inappropriate because again this is labelling children too early. Many children questioning their gender identity stop during puberty, so let them go through puberty before expecting them to pick labels.
So yes, if I lived state-side, I'd join this boycott, not because I dislike LGB or trans people, but because I think that applying queer theory and sexuality labels to children is flat wrong and harmful to the children.