Firstly, I guess it depends on where your Crohn's is active or what part of your bowel is still intact as to whether or not you can absorb B12 from your food. If that part of your bowel is badly scarred from past inflammations or has active Crohn's in that area or if it's been resected out, you will gain no benefit from taking B12 orally. Secondly, I'm not sure why COVID would have made any difference to B12 absorption making it more efficacious to switch from injection to oral. That, to me as a lay person, makes no sense. I would certainly ask your Gastro about it. If you haven't had your B12 levels tested, I'd consider asking them to do so.