Yes very true, most of the SEC is not at Bama or Georgias level because obviously Bama and Georgia are going into those other southeastern states and taking their best players. Those SEC teams are also still better than 3-14 in other conferences.
I spoke to a friend of mine who's a coach and he says that the internet has made the Southeast that much better at developing teams. The schemes and strategy that once made Ohio great is now not a secret all over the country and it's being used by places that have more practice time and better athletes.
I audited Georgia's roster and a little over 80% of their roster is home grown. I'd have to go back and cross reference out of state players on their roster who directly contribute to their on field success. That being said, I'm going to wing a guess that Georgia's success has more to do with the athlete's in their state and that they are not really poaching anyone of any significance outside the state of Georgia. Based on that it would seem spring ball has less to do with their success, although I don't know how many days they get in May. They may get more for all I know.
GA's success has probably more to do with an ever increasing population of internal migrants from around the US and well finally finding a HFC who can get the job done (no offense to Mark Richt).
More practice time yes. Over a high school football player's career in South Carolina they are totaling 60 additional practice days. However I can tell you first hand those first 3 days are spent making sure kids have paperwork turned in and sizing kids for equipment and helmets.
With regards to better athletes you and I could make the same argument if it were the 1920s, 30s, 40s and 1950s / 60s when the "rust belt" was still brimming with large populations (better athletes).
I would argue the air conditioner played more of a role in opening up the South to what was going on up North. Without AC ain't no way anyone from up North is moving down here.