It is possible for the extruder to load fully, but it really depends on the head position, as it'll sometimes hit inside a small space between the tube holder and the inlet.
Another issue I cun into is I've never used Prusa Slicer before, I would rather have used cura at this point if I could, but the generator doesn't work for the MK3 yet.
For reference, with the printer being direct drive, I had to mount the unit lower than the print head and hang the tubes up in the tent this printer came with.
If anyone managed to get this to work with the reborn 2 or ghost 6, as they use the same extruder. Tell me how you did it as I'm having issues just getting it to load sometimes