I saw this and honestly didn't get it. NFA items have been good to go for decades in TN.
I did a little digging, and it may just be some housekeeping/ fuck you feds and not actually groundbreaking laws. SBRs were illegal at a state level unless you had a fed tax stamp. I believe that is the "big" change. So, for most people that don't want to risk residing in federal prison there is no difference.
TN county sheriff kicks in the door of your meth lab and finds a SBS with no tax stamp. Two deputies having a conversation; "Well shit Cleetus, we cant charge him with no crime for the sawed off shotgun nomore" "No biggie Jim-Bob, I know Earl over at ATF ov' dare in Nashville, lets call him up"