I get very bristly at this idea that boys are having their freedoms restricted by the limitations on their clothing choices being more restrictive than for girls.
I think you'll find in general that if a member of an underclass in a liberal society dresses like a member of an oppressor class, you'll see most of society nod politely at the attempt, even if it's a bit badly pulled off. When a member of the oppressor class dresses up like a member of the underclass, it's seen as weird and not very nice to do.
If a recent refugee managed to get a donated suit from a banker and wore it with pride, that'd be lovely. If a banker decided to dress like a refugee and walk around in rags, people would think it was very strange. When university students who are quite rich "slum it" and pretend they are poor a la "Common People," it's an ugly thing to do.
The same thing is true for clothing belonging to specific racial minorities. A black person in clothing most commonly associated with white people, using an accent most commonly associated with white people, isn't even something most people would notice or comment on. Even lightening your skin is very common in some cultures. But a white person deciding to wear cornrows and dress in black-associated fashion brands and trying to use "urban" slang associated with black people would be considered a creep, and rightly so.
Boys are restricted because they are the oppressor class. Offering boys a choice of more clothing and saying "oh, the poor boys, they long to wear a princess dress and cannot" is putting boys on even more of a pedestal than they already are!
It matters a great deal to women that boys are taught to be "gender neutral" about things like childcare, cooking, cleaning, emotional labor, "the mental load" of planning for a family. Perhaps once we have a generation of men successfully engaging in these activities, we can worry about opening up the princess dress as a wardrobe option?
It really chafes to see a thread about a little baby girl being treated badly result in so many "what about the boys, what of their love of pretty colors and objects?" replies.
What all this sounds like, applied to any other category but sex:
"It's so important to end racism, that's why we let our children get their hair done into little braids when we went to Jamaica!"
"It's important to end ableism, so we want to make sure our able-bodied child knows it's perfectly okay to go to school in a wheelchair if she wants to, it's her choice and no one can tell her otherwise."
"Marie Antoinette is using her identity as a classqueer woman to break down performative boundaries between peasants and royalty."