AnyConnect uses a point-to-point tunnel interface to establish the connection, so your gateway address for secured routes is going to be the same as your assigned address. This is normal.
To give you an example, I have connected to my own AnyConnect router and received IPv4 address 172.31.4.11. When I do a "netstat -rn" and check the gateway for my secured routes, I get the following:
Internet:
Destination Gateway Flags Refs Use Netif Expire
172.23/22 172.23.4.11 UGSc 0 0 utun0
172.23.4/24 172.23.4.11 UGSc 0 0 utun0
As you can see, the gateway for my secured routes matches my assigned IPv4 address.