Also, If you LT pace is any slower than 1 min slower than race pace, than that would be an easy run, and totally defeat the purpose of stretching you Lactate threshold because there would barely be any accumulation. ...Also, if it is any faster than 1 min slower than race pace, then that would be TOO much lactate accumulation.
It's a steady state ( not going above LT and not dipping below), and 1 min slower than race pace gives that steady state better than any other pace regardless of the distance.
By the way, did you even watch this video? Daniels himself says "LT is A SPEED at which lactate production & clearing balances. Any faster than that and lactate rises, any slower and lactate lowers. Train at that speed. Not above it. And not below it"
A SPEED. A SINGLE SPEED. Does not change with duration of workout.