System Information in 5G NSA vs. SA Deployment
In NR non-standalone (NSA) deployment, the UE does not necessarily need to receive NR system information blocks (such as SIB1) or any NR paging messages because all the information can be sent to the UE through LTE control plane signaling in connected mode when the 5G Secondary Cell Group cell (SCG) is added.
However, in NR standalone (SA) deployment, the UE is required to read the Master Information Block (MIB), Remaining Minimum System Information (RMSI such as SIB1), and all Other System Information (OSI such as SIB2, SIB3, etc..) during cell search or for other idle mode operations.
Source: MediaTek