U will get average SR after first placements (around 2200sr) but u can be lucky so u can get ven more .. than u can fall to your real rank .. Its common that bronze noob can get gold or plat on smurf thats why I hate newbies because they arent on their real rank
It's understandable getting placed on low ranks and be stuck there on your first attempt(cause you weren't ready) can then lead to beeing placed higher on an alt account since this time you are more prepared, and that's what get a lot of people mad