That's not exactly true though, your node and the peer you anonymously connect to can both be clearnet for Tor. You just need a tor proxy available to your node and it can route it through an exit node.
Similar for I2P, except the peer must be behind I2P as well.
It breaks all heuristics if used today for any transactions sent with it. For dandelion, you need many peers running it to hide in an anonymity set.