I'm sure the metric controls for sample size, otherwise it would be a very flawed statistic, as you implied.
looks like last year 60% of the top 10 teams in that stat did not make the playoffs (NYG, OAK, CHI,NO, KC, ATL)... so i dunno there might be some flaws to that logic.
I'd much prefer to be #1 than #32, thats for sure. Having said that, this stat doesnt equate for how often a team gets there, which I think is much more important.
You have to look at a couple of stats for it to have some real meaning. The top 4 teams in RZ TD % are also 1, 2, 3 and 8th in RZ attempts. But that being said, stats don't win games.