M4 Origination Points

Origination Point is connection from some initial entity (device/line/trunk/provider/supplier/etc) where call starts/originates.

Call comes from Origination Point and goes to Termination Points.

Why there is no Register option on Origination Point?

Registrations are needed when Dynamic IP addresses are used. Dynamic IP addresses are very common on Retail business, but not on Wholesale. That is why M2 does not have such option.

You as a system owner can allow traffic from IP:Port:Technical Prefix. This is enough to receive traffic from any OP.