And further on with the same topic now as I got into speed;

4G networks (which actually are called UMTS Long Term Evolution, or LTE for short) are structured a bit differently from the earlier GSM and 3G networks. On the backhaul side they do not have ATM any longer but are connected to the core with IP routers only.

This is the reason there is no CS call possibility in LTE, and your only option for a voice call is either drop the connection to either 2G or 3G or use VoLTE which is an end-to-end IP based call.

The same thing goes with 5G, just like LTE it has IP only backhaul and core and similarily only supports IP calls.