S&W 686+ 3"

looking at possibly getting my first wheel gun and considering the 686+ in 3". When I look online and give my LGS the SKU it mentions MA compliant but I don't see that designation for the 4" or 6". I realize that by design the DA has higher than a 10# trigger and holds less than 10 rounds. Just curious why the 3" carries the MA compliant designation? Is it different other than barrel length than the 4 and 6? When i called my LGS and gave him the SKU he said "You know that's the MA compliant model don't you?" But there is no other SKU according to the S&W website. I don't live in MA and doubt I'll ever go there just wanting to make sure there's nothing different about the 3". I understand semi auto differences for MA compliance.