I do not think it will harm it and I believe many people do it. Plant there seedlings into there final pot to avoid any shock from transplanting. However, I prefer to have a smaller pot until it gets big enough to go into a larger pot size. This allows me to water and add nutes more often versus watering once every 2-3 weeks. I also have never experienced any transplanting shock, where the plant is stunted for a few days after transplanting. What I have always noticed is that once I transplant, the plant seems to take right off and have a minor growth spurt.