Renraku Waza, also called Renzoku Waza, are combination techniques.
You could also say that they are applications of the basics.
Fundamentally speaking, the fact that it is an application means that the core ingredients are already present in basics. You can argue because of that, whether there is a strict necessity to practise Renraku Waza...
...I would argue in favor of the motion.
Renraku Waza teaches you continuous movement which are present in basics, but must be drilled into your body by physical practise.
I had to learn the hard way about the full meaning of Renraku Waza, after throwing away the chopsticks.