Why would payloads already be encrypted?

[natevw]

All payloads are encrypted before transmission regardless of if they are already encrypted.

My understanding is that this is facilitate consistent packet handling, so the requirement makes sense but not sure why its highlighted here. Under what circumstances might you expect an example of doubly-encrypted transmission to happen? Doesn't seem like you'd try forward HTTPS or something over a TMesh link to begin with due to its throughput.