That is correct, if you enable private networking on both droplets you should be able to ping directly between them.

However, both droplets need to be in the same region to be on the same private network. If they are in different regions then it won’t be able to ping between them.

You can also find a lot of information here in our product documentation for private-networking:
https://www.digitalocean.com/docs/networking/private-networking/