"clean as possible" as in "no trace of custom firmware" (as implied by the reference to RMA) does not require a restore factory default operation. Just picky.
I might not have bothered, if the instructions initially posted in reply had been accurate in other respects. Also, in my opinion it is better to point people at the standard references than to keep re-writing them. It is no less helpful, and allows the effort to go into improving the references rather than allowing a variety of versions to be extant.