Not necessarily. See the "carbnite" thread in the semi low carb subforum, even some people on otherwise very low carbohydrate diets do some high carb days, but scheduled. That's probably safer than just doing a spontaneously higher carb day. I don't think even planned high carb days are for everybody, a lot of people can end up on multiple day binges or even of their plan altogether, but some people do seem to do just fine with it. Being on the best diet that you can sustain is more important than being on the best diet possible, since no diet can do you any good unless you're actually on it.

Only your body knows if this approach will stall your weightloss, only way to know for sure is to try and see, and remember to change tactics if it doesn't work or eventually stops working.