@JohnSmith6429: It's *maybe* true in that context (< K5), as some devices did ship with USBNet enabled in diags.
In main, never, though.
EDIT: Or, hell, maybe in some antediluvian FW releases. Generally, no, though. Will update the wiki, as it's confusing, and easy to spot up there at the top ;p.
EDITē: Technically, for those specific JB exploits, it is based on a legitimate update (parts of it, anyway), so some of it may be untouched and signed by Amazon

. But that'd be nitpicking, as we did not re-sign anything ourselves

.