Yeah but doing that really delays your rush, so it won't be a rush at all. It is very situational with Germany, sometimes you don't get to clear too many camps, and even if you do, you are not guaranteed to get units from them. In one game I cleared all the camps I found, and got 2 units out of them. You can gather a decent military, but will it be soon enough to do a CB rush? Maybe an XB rush could be performed, but you really need to get lucky with camps.