The lye continues to have an effect even after you stop the current. Leaving it in the follicle before removing the hair can be gentler for your skin and can help with avoiding overtreatment and managing pain. I almost always leave the lye to sit in the follicle when doing slow blend while I continue on to treat other follicles. It means I can use lower settings and less exposure time if I want to be gentle.
I mention this because others who have posted about their DIY experiences with galvanic epilators tend to overtreat resulting in very large scabs which are temporary but still unfortunate.