All files on a commlink that are not protected / encrypted are viewable to anyone that can see your commlink within the matrix. You don't need a mark on the device, but to copy/delete/edit the file you need a mark on that specific file icon (on each individual file icon you want to copy/delete/edit)
SR5 p. 222 Life with a Commlink
Most of what you keep on your commlink are files, this includes music, your SIN (fake or otherwise), licenses (also fake or otherwise), maps, email messages, your contact book, AROs, and so on. These files are visible to people who can see your commlink in the Matrix, so most people keep all of their files in a protected folder.
The BK example is likely wrong in that he should technically place a mark on the non-protected file icon itself in order to copy that specific file (but the test would be resolved and opposed in the same way as if placing a mark on the commlink so it doesn't really make that much difference in this case).
In SR6 access is per network, not per icon. To take the Edit File action you would first need to gain access on the entire PAN (or the Host) rather than just one specific file or one specific device. Having access on the network give you access to all resources that are part of that network (all devices, files, ...) - this speeds up the action economy quite considerably :-)
Same as in SR5 you can take the Editor complex form on a file without having access. But same as in SR5 when it comes to files located inside a host you still might need to first gain access on the host in order to actually enter it (either by taking your time to probe the host and then silently sneak into it via a backdoor or entering the host via the main gate either because you had legal access or by loudly brute forcing your way in to gain illegal access).