When you really think about it, if we are talking about a Radiant instead of a human, they would regrow the limb automatically. Kaladin, being a Windrunner, does not have the surge of Progression, yet he can still heal the Shardblade wound that I believe severed his arm. All KRs have the ability to heal to a certain extent. If their arm is severed, by a Shardblade or not, they will heal. And in the case they don't, a Radiant with the surge of Progression could heal their arm for them. I'm going out on a "limb" if you know what I mean.