Have never needed ID to buy SJ tickets either. These days you can guy regional tickets from the new machines without even having to provide a name. Previously the name you provided could say anything and was never verified. Probably a remnant of a Swedish law that was followed to the letter, not realising how retarded the out come is.
OT: MTR will be taking over regional traffic in Stockholm in the future, it would be interested to see if that allows the accumulation of EB points and at what rate.