To verify this, use FTP or SMB in the guest operating system to transfer a file. Check the transfer rate, which should show that the virtual network adapter is not limited to the 10Mbps limit reported in the guest operating system, as the external network is faster than 10Mbps.
The guest operating system reports the 10Mbps speed because the virtual network adapter is an AMD PCnet II compatible NIC, which by definition is a 10Mbps NIC.
Even though the virtual NIC identifies as 10Mbps, it actually runs at the higher rate of the NIC within the ESX host.