There is no excuse. Whether you rehearsed for 30 seconds or 30 years. A performance is a performance and should not be judged for ANY other reasons.
Professional dancers won't even tell you that they did that. I am a professional dancer myself and sometimes me and my group come up with performance at the last minute. But we don't go around and tell everyone that we do that. Nor is it an excuse for us to be judged less harshly.
If your going to get on a stage then you need to work it. Nobody cares if your sick, or if you had 1 minute to rehearse.
Nor should anybody be given extra credit for having less rehearsal time.