It is not recommended to manually register drivers, it is better to allow them to load themselves when the Class is loaded as happens with Class.forName()
The source for the DriverManager is available with the JDK, and if you have a look at it, it doesn't manage drivers well since manual loading can produce duplicate entries.
My answer is: maybe, but I'd have a look at the source to make sure. Normally I wouldn't recommend looking into the source code to solve a problem, but the behaviour is not specified in the API