No VoLTE is not the same as VoIP (Skype, etc).
VoIP (Skype, etc) rely on the 'Internet' to deliver packets which is done on a “best effort” basis while VoLTE uses the IP Multimedia Subsystem (IMS)
IMS or IPMS does not require NAT, traffic routing etc.
Disabling data (internet) won't stop you from making voice calls but disabling VoLTE will stop you from making voice calls because Jio has only IP switching and not circuit switching