That depends - while it's allowed in the regulations, some people (me for one) aren't happy burying crimps in walls (which is what it sounds like will be needed). It also depends on the size of the cable, whether he can get appropriate crimps for it etc etc.
I can understand him wanting to run a new cable, as with a high power appliance, any joints are weak points, and if it's not a perfect joint, it will heat up when high currents are drawn, and could at a random point in the future melt, causing at best an intermittent fault, at worst a fire.
He also may have wanted to re-run it because he may have spotted the existing cable is undersized or whatever - basically you'll have to ask him - I'd say just suggest to him about crimping it, or putting in a high rating junction box under the floor etc, and see what he says...