The baseband component carrier waveform in this example is characterized by multiple subcarrier spacing (SCS) carriers
So this example uses multiple subcarriers.
The two elements of scscarriers is because the example uses {} with two nrSCSCarrierConfig -- you could use 1 or more than 2 if you wanted.
https://www.mathworks.com/help/5g/ref/nrwaveformgenerator.html nrWaveformGenerator indicates,
[wave,info] = nrWaveformGenerator(cfg) generates 5G NR waveform wave for specified configuration cfg. The input cfg specifies either downlink or uplink configuration parameters for single or multiple subcarrier spacing (SCS) carriers and bandwidth parts (BWPs).
So it specifically says that it is acceptable to use single SCS for it.
The answer would therefore appear to be that No, it is not mandatory to use two carriers -- you can use one or more carriers.
