To the best of my knowledge, peanuts and runts are different. Peanuts occur in dwarf breeds, where dwarf rabbits are bred, you have a chance of getting peanuts (more chance with two true dwarf rabbits than one or two false dwarf rabbits). Peanuts have a poorly formed hind end and as far as I'm aware, they don't ever survive. While runts often struggle, they are simply smaller, whereas peanuts seem to be not quite properly formed, something to do with getting two pure strains of the dwarf gene or something. A poor explanation, but I think I got the basics of it. Someone will know the proper terminology and reasoning.