I’m a little bit late, but here is my answer to the “dirndl dress” question.
I sewed three 1950s dresses with dirndl skirts this year. One is Simplicity 3429 which I made twice.
I do own a few vintage dresses. At least 3 have a true dirndl skirt. A few of the others dresses have pleated skirts, but they are made from two rectangles too.
I try to post pictures of them on my blog in future, because I think it’s always interesting to see how things are done back then.
You can read more about Simplicity 3942 and “dirndl dresses” in general here.