I agree. That selection of photos seems to be confusing stage or screen wear, lingerie and sportswear with daywear.
You could probably go even further back to the Victorian era and find a picture of a stage performer in a short skirt, something that no respectable woman would have worn on the street! But I don't think it would equate to the mini, which was a popular fashion worn by many women in their regular day-to-day lives.
Although I do agree with Louise that Mary Quant was very probably influenced by 1920s fashions. Some of her early 60s dresses - pinafores (jumpers for US viewers!) with dropped waists and short pleated skirts, especially - are very similar to 1920s examples.
Sarah