No, the ASA is not capable of doing reverse lookup and determine who is using an IP because the DHCP pool is basically a pool of ip address, and it is not a static IP Address allocated to the machine. Therefore, even if the ASA is capable of doing a DNS lookup, and since the DHCP pool is just a random address which is assigned when user connects in, there will be no dynamic DNS lookup because ASA does not have a list of all the machines' name with its assigned IP.
In summary, ASA does not have the capability of performing reverse lookup of the machine name for those connected via VPN.
