Well I guess to each his own but its the way I always been taught. I guess the real reasoning is that you dont look lumpy onstage after depleting and such.. I mean I know people that ran up til the day and had no problems so I guess whatever works best for you.
I see what you're saying, but I believe this "lumpy" problem is due to diet, not running oils to the day. True, if you get crazy and insane with your carb load and all the final prep, the combo of that and the drugs is going to cause some problems, but the true problem is the insane way some people take their final prep. If anything running your stuff to the day should be a positive, it should help keep you fuller, tighter and harder.
I think the "lumpy" you're referring to is really caused by guys simply spilling over with their carb up.