This is partly dependent on the speed of the drives. Does the dvd-rom drive read at the same speed or slower than the dvd-r/rw can write? If the two speeds are too close the program may consider it too close a call and prefer to rely on the hard disk. There’s also other factors to consider, such as processor power, memory, background tasks, etc. If you do on-the-fly recording, a tiny slip during the read/write operation can ruin the whole dvd-r/rw.
Here’s an idea though: if you can set the write speed to be low enough (half to 3/4 of the dvd-rom reading speed?) perhaps the software will allow you to do on-the-fly recording?
