When you make laws such that nobody knows where the line is, people will step over it. Always. They do.
That is all laws all the time, ever. From the 10 commandments on down to modern meat processing regulations.
According to this, a woman in a miniskirt with no underwear is not 'partially nude'. Now, don't try to tell me "But... but... it says 'covering these parts'" because if it is covering those parts adequately then they can't be photographed anyway.
Unless all your clothes make an air tight seal around all the openings for your limbs, there will be angles and circumstances where we'll be able to see what's inside.
That possibility doesn't constitute permission to manufacture those circumstances and then exploit them.
"But... but... it says 'covering these parts'" because if it is covering those parts adequately then they can't be photographed anyway.
And then on top of that there is 'infrared' cams and other clothing penetrating photography? So now unless all your clothes are made of thick wool with airtight seals then any creep can put closeups of your genitals online? Hardly. Its pretty clear to any reasonable person that the infrared or upskirt photographer is effectively stripping them of (some of) their clothing for the purposes of the photo, rendering them 'partially nude' even if they don't actually take anything off.
Frankly I'm actually surprised the the judges didn't see it this way. There was quite an uproar about the TSA 'nudie scanners' after all; but apparently those security (theatre!) photos weren't (partial?) nudes after all, so what was everyone whining about?
rational people DO draw lines
Right, but they draw them where they want them to be, not where its most convenient to interpret them. Your argued that the only place we should draw lines are such that they be easy to rule on instead of reflecting what people actually want.