I thought they only took one for each body part, so either skirt, trousers or loincloth, but not a combination of lower body wear.
They'll claim (and if possible wear) one for each _layer_ for each body part. I.e., both "under" and "over" for the feet - socks and shoes; "under", "over" and "cover" for the upper body (e.g. shirt, robe and cloak). For the lower body/legs, there are three "under" clothing types available - thongs, loincloths and braies. If any of those become available, dwarfs will claim them and put them on. And they'll commonly wear them until they fall apart. In addition, "over" clothing will be worn, like trousers and skirts. Outside of military uniform assignment, they won't take multiple items for the same body part and layer, though - a military dwarf may be able to wear three skirts simultaneously, a civilian dwarf will only wear one.
I've jsut dumped a whole bunch of freshly made clothing into a room full of unclothed dwarfs.
No one is picking up anything I think they must all want goblin clothing from outside which they aren't allowed!
You can check clothing ownership through the normal display - 'v'iewing an item will display its owner. This holds for loose items that have been claimed but aren't worn (yet). Dwarfs who try to equip fresh gear will claim an item first, reserving it for their use, before they actually pick it up and try to wear it. This leads to soldiers with no-clothes uniforms regularly claiming clothes without ever wearing them, thus blocking them for the use of civilians.
Looking at a dwarf's general information screen ('z' from unit view) also shows their 'owned items', which currently means nothing but their civilian clothes, both claimed and worn. It only mentions the number, but if a naked dwarf boasts 14 owned items, you can be sure they've _claimed_ a full set of clothing, they just may have trouble getting hold of it.
I wasn't aware that clothing claims ignore pathing, but it doesn't surprise me in the least.