I'm not from Lenoir City, but I think I can answer your question. Holding spring practice early serves three purposes:
1. Avoiding the crush of spring sports - get it done before track, baseball, soccer and tennis start and pull off key players.
2. Getting rid of the "wanna-be's" - there will always be new kids who want to come out and do the weightlifting and enjoy all the camraderie of the weightroom and then quit after one or two days of actual practice. Having spring practice early allows a coach to find out which of the new kids really wants to play football, instead of just being "iron groupies". That way, you don't waste 5 months training, conditioning and working with a kid who is just going to quit on you.
3. Ironing out any new offensive/defensive system changes - tweaks, or sometimes wholesale new installments of schemes need to be tested early to see if they fit the talent or if indeed they are worth pursuing. There is nothing worse than working 5 months on a scheme/technique that turns out doesn't work on the field.
Several schools in the area hold spring practice relatively early, most notably Maryville. Seems to work for them.
Just my two cents.