Nowhere in this article about the Packers' defense scoring lots of touchdowns does it wonder whether it's actually a skill as opposed to, you know, a fluke. God knows the Elias Sports Bureau isn't going to tell the author.
The Packers have seven touchdowns in ten games. It's a good figure -- only one team since 2001 has had more than seven touchdowns in an entire season. It was the 2007 Minnesota Vikings.
This year? Through ten games, those Vikings have exactly two defensive touchdowns: A fumble recovery and a blocked kick, both returned by Antoine Winfield for touchdowns. (They also have two safeties, although that's beyond the interest of the article.)
It's not an isolated trend. The league leaders one year simply don't do well the next. The '01 Dolphins had six defensive touchdowns in 2001, one the next year. Tampa had five in 2002 and three in 2003. New England and St. Louis each had six in 2003; they had four and three, respectively, the year after. Baltimore had seven in 2004 and three the next year. San Francisco had five in 2005 and one in 2006. Baltimore again took the lead with six in 2006; they had one in 2007.
It's simply not a consistent skill, at least on a team-wide basis.