That would appear to be correct. The directory does not exist at all on my phone and hence the mv command above will silently malfunction.
Slightly safer is: sudo mv -t /lib/firmware RS9116_NLINK_WLAN_BT_IMAGE.rps
so that it either does what I want or fails with an actual error message (at the cost of specifying the source and destination arguments in the opposite order as compared with what we have been doing for a thousand centuries).