SSB GSCN is the center frequency number of an NR cell. SSB GSCN stands for "SS block group-specific cell number" and is used to identify the center frequency of an NR cell. This value is used in combination with the operating bandwidth of the cell to determine the physical layer resource grid for the cell. As such, it is important for the correct SSB GSCN to be configured for the cell in order to ensure the correct channel coding.

Making 5G NR a Commercial Reality A unified, more capable 5G air ...

https://www.qualcomm.com/content/dam/qcomm-martech/dm-assets/documents/powerpoint_presentation_-_making_5g_nr_a_reality_february_2020_web.pdf

GTI 5G Device Power Consumption White Paper

https://www.gtigroup.org/d/file/Resources/rep/2019-07-05/cbf7810256b4c312c460863fcb77bd58.pdf

In 5G NR, the SSB (Secondary Synchronization Signal Block) is used to provide the time and frequency synchronization information to the mobile devices. It is transmitted in the frequency domain and it consists of two parts: the SSB GSCN (Secondary Synchronization Signal Block - Group and Sequence Number) and the SSB MIB (Secondary Synchronization Signal Block - Master Information Block).

The SSB GSCN is a unique identifier that indicates the center frequency number of the cell. It is used to identify the cell and to determine the frequency offset of the cell with respect to the carrier frequency.

So, the statement is true, SSB GSCN is the center frequency number of an NR cell. It's worth noting that the SSB MIB contains other system information such as the system bandwidth, the transmission bandwidth configuration, and the number of symbols in a slot.