It's true, bracketing only allows one stop increments (a long running complaint about all the Nikon pro bodies).
I could be wrong as it's been years since I used a D70, but I believe the D70 allows a bracket of 3 shots, with up to 2 stop increments, allowing for a +/-2 stop bracket.
The D700 allows up to 9 shots with 1-stop increments, which gives you +/-4 stops. This is a wider range, but you need to take more photos to get it. Setting the D700 to 5 shot/1-stop bracket gives you the same +/-2 stop range, but you need to take 5 instead of 3 shots to get it.