If both sides of your ssh tunnel (pub,private keys) are under your control, in theory, that's "zero trust".

Unless one considers the meta data such as src/dest IP are visible to Tailscale sw.

Right?

'Zero trust' has a technical definition that's not really relevant here. See: https://en.wikipedia.org/wiki/Zero_trust.

The concept is separate from 'zero config' (https://en.wikipedia.org/wiki/Zero-configuration_networking), which Tailscale's low technical barrier to entry evokes.