Nowadays we don't actually armor legs unless you're talking bomb squad.
It is acceptable a loss of limb of a soldier during a war, that's why most armor since inception has a skirt of sorts to protect the groin and upper thighs due to the lethality of blows to that area.
But to reply to your points:
Those aren't womens' wear.
Armor has always been unisex, only exceptional cases where they have been made to high paying customers were them made "female"
Those aren't dresses and they're not skirts either.
All of the examples have groin/thighs coverage in a skirt way. Be it a chain mail with plate or the striped skirt of the roman armor.
You don't wear any of those without leg armor. Saying armored skirts "came before" might be relevant in a FeudalPunk setting, but I don't feel like it is in this one. Maybe you do.
Most of these were actually worn without leg armor under it. Romans wore sandals with grieves on the shins. Japanese used shin guards and sometimes a longer skirt that reached the knee, but with cotton pants under it.
Those designs are centuries old and aren't recapitulated in anything contemporary - NOT EVEN now that women are present in fighting, security and defense forces, which wasn't even true at all way back in the years when those pieces were in use. Show a modern one or a futuristic example if you're actually trying to be persuasive.
Current personal protection equipment consists mainly of bullet proof vests. Personal armor is usually only worn on the chest as it is where all vital organs are. You can get a lethal blow to your limbs but a tourniquet and amputation will prevent you from death. And "even now that women are present in fighting", they actually were in the past as well, they just wore the armor at hand. All armor is made unisex as it is to protect internal organs, not to look good.
The difference in Sindome is that we take "style over substance" and do the dresses and skirts because in the theme it makes sense for a line of armored clothing to cater to women's design desires, niche market and all that.
I understand you don't like, but saying it breaks immersion or is surreal is not correct since skirts as armor existed before any pants armor.