That's what I'm doing regardless of when the cache is published, and I've never had any problems with that.
I can't find any guidelines specifically about logging challenges, but there is this said about virtuals and earthcaches: "Send your answers by email or Message Center directly to the cache owner. (Note: cache owners cannot require information to be sent through one particular tool.)" I would say that sending challenge owners documentation about having met the challenge criteria from the checker and not via their choice of tool is well within the spirit of the above text, even though it's not specifically mentioned.