Does google encrypt data in transit inside vpc? Came to know from a multicloud vendor that , all 3 public cloud doesn’t encrypt in transit data.
I don’t think there any form of encryption for internal traffic within VPC. Internal-VPC traffic will traverse entirely within the perimeter of the backbone network of cloud provider (GCP in this case), therefore encryption in this case is quite redundant. Each cloud provider, GCP included, have their own commitments about data privacy and necessary standards for data privacy, so basically when you use services of a cloud provider you need to have some implied trusts in them ;).
Of course you can implement your own measure of encryption, e.g. implement IPsec tunneling between Subnets in VPC, but that will create lots of overheads for your traffic and somewhat slows down your network performance.