Or does route-based IPSec VPNs tunnels always imply using VTIs?
In my somewhat limited IPSEC VPN knowledge, an IPSEC VPN itself has no virtual tunneling interface capability. It just ciphers packets from a source/destination pair by creating a security association.
The VTI was created so that it was made easier to be able to put traffic into the IPSEC VPN as well as to run routing protocols. Original policy based security associations for IPSEC VPNs didn’t have those capabilities.
Yes, at least with other vendors it does. Never done it with Cisco.
What? I’d say D-VTI is less common than normal static route-based IPSec’s (which is absolutely possible).