When I see/hear about a team that has great second halves, it begs the question - why didn't they do that in the first half? Maybe because the other team eased off on defense, at least some, after they got a lead? So the "comeback" team didn't really do anything much different, the other team let them off the hook somewhat.
To me it's similar to bragging about some quarterbacks "comeback" victories. Wouldn't have to "comeback" if they took care of business in the first half. How many NFL teams have had the moniker "Cardiac..."? I remember the 1970's "Cardiac Cardinals", in 1974-75 they went 10-4 and 11-3 with stirring comeback victories, only to lose in the first round of the playoffs both years, e.g.
Maybe in the "modern" NFL teams can too easily roar back in the second half, with the current rules, and getting ahead and staying ahead is more difficult. But that's what I'd prefer to see...