I would guess it depends on how severe the disease is presently in the person in question. Crohn's disease is not something that affects everyone the same. Some have it mildly while others have it more severe. I agree that steroids can be of great help to individuals with Crohn's providing the steroids don't cause any worsening of the disease.
I was diagnosed with colitis last year which is similar to Crohn's though limited only to the colon. I was put on prednisone as well and I would not wish that drug on anyone. I finally got healthy again and was able to get off of the drug but I currently have oxandrolone on hand for any future episodes. I refuse to watch my hard earned muscle go to waste because of a drug I'm taking. It won't matter how hard I workout or eat, that drug is catabolic by nature and you can't beat it with diet and exercise alone. I will use a mild morning only dose of Ox which is one of, if not the best, anticatabolic drugs out there. At least it will give me a fighting chance.
In general though I'd say it's worth a try and if it doesn't cause any more inflammation than normal then it's probably ok. I have done a few mild cycles since last year with no problems including ox, fina and currently Dbol. So far they haven't causes any abnormal gastrointestinal sides so I'd say for me they aren't a problem. Doctors told me my colitis was mild though so someone with a severe case may have different results.