i believe the answer would be “no” – there are people on this forum with intimate knowledge of the technical side of both w/ and real life tape machines I’m sure but I’ll answer as best I can:
what w/ does is replace the erase head (in the tape metaphor) with an attenuator. -5V puts the attenuator before the read head, +5V puts it after the read head with everything in between lesser degrees of attenuation in both directions. As the manual describes it, w/ itself is doing the same action both direction, we’re just listening to the tape before attenuation rather than after. I guess this could be thought of as moving the play/read head as you said, but not in relation to the write head because it doesn’t affect how you’re hearing new material coming in - only looping material.
the video tutorial and manual are both really really good, and maybe there’s a technical map on the way too 
i reckon mods will move this whole convo to the w/ thread, but figured i’d answer here for now.
edit: here’s the section of the tutorial video that talks about this