It depends, but mostly - YES - if you are cutting your own pattern for a circle skirt, or even a bought one, parts of the circle are going to sit on the bias grain - bias grain will stretch more & therefore will "drop" making that part of the skirt longer that the bits that sit on the straight grain IYSWIM
Different fabrics will give more, some less so, so it really depends on the cloth, but the fabrics with the most give, these are the fabrics such as georgette, which also give the best ruffles, as the hem will also stretch well but will likely "drop" quite a bit in length on the bias grain
Sooo - if for example - if you cut a circle that is say 30cm in length all round - the bias grain could drop by say 3/4cm, making the sides of your skirt longer than the middle by 3/4cm - this will look even worse if you have several layers all coming up at different lengths - IYSWIM - Levelling your hem after hanging over night, solves this problem & gives neat even length layers to your skirt.
You can also cut "ruffles" these are shaped like spirals, so you get several bias grain areas around the hem, these are less likely to need levelling, as it wont be so obvious as a couple of inches bias, next to a couple of inches straight grain repeating around the hem - but these are not easy patterns to make yourself, as working out the narrower waist measurement or panel measurement to fit a spiral with the needed wider hem measurement takes a lot of skill to work out - I know experienced pattern cutters who would struggle with this sort of pattern, so unless you buy a ruffle pattern I wouldn't recommend this as a solution